The copy_audio_data function really shouldn't be inlined because it's
being called twice.  It's somewhat unnecessary, I think I left it inline
by accident.

This flag is actually useful under a number of circumstances, and has
been requested a number of times.

This changes the way source volume handles transitioning between being
active and inactive states.

The previous way that transitioning handled volume was that it set the
presentation volume of the source and all of its sub-sources to 0.0 if
the source was inactive, and 1.0 if active.  Transition sources would
then also set the presentation volume for sub-sources to whatever their
transitioning volume was.  However, the problem with this is that the
design didn't take in to account if the source or its sub-sources were
active anywhere else, so because of that it would break if that ever
happened, and I didn't realize that when I was designing it.

So instead, this completely overhauls the design of handling
transitioning volume.  Each frame, it'll go through all sources and
check whether they're active or inactive and set the base volume
accordingly.  If transitions are currently active, it will actually walk
the active source tree and check whether the source is in a
transitioning state somewhere.

 - If the source is a sub-source of a transition, and it's not active
   outside of the transition, then the transition will control the
   volume of the source.

 - If the source is a sub-source of a transition, but it's also active
   outside of the transition, it'll defer to whichever is louder.

This also adds a new callback to the obs_source_info structure for
transition sources, get_transition_volume, which is called to get the
transitioning volume of a sub-source.

The reason to keep a reference counter for transitions is due to an
optimization I'm planning on when calculating transition volumes.  I'm
planning on walking the source tree to be able to calculate the current
base volume of a source, but *only* if there are transitions active,
because the only time that the volume can be anything other than 1.0
or 0.0 is when there are active transitions, which may change the base
volume of a source.

Changes OBS_SOURCE_UNBUFFERED to OBS_SOURCE_FLAG_UNBUFFERED to make
naming a bit better for source flags.

When the presentation volume is set for a source, it's set for all of
its children and their children.  The original intention for doing this
was to be able to use it for transitioning, but honestly it's just bad
design, and I feel there are better ways to handle transitioning volume.

Adds a signal is called when the sync offset has changed for a source.

Changed the design from using obs_source::enum_refs to just simply
preventing infinite source recursion in general, rather than allowing it
through the enum_refs variable.  obs_source_add_child has been changed
so that it now returns a boolean, and if the function fails, it means
that the child cannot be added due to that potential recursion.

..Apparently I left this function unimplemented.  This function just
returns whether a source is currently active or not.

Remove the calculation of volume levels and the corresponding signal
from obs_source since this is now handled in the volume meter.
Code that is interested in the volume levels can either use the
volmeter provided from obs_audio_controls or use the audio_data signal
to gain access to the raw audio data.

This adds a new signal to (audio) sources which is emitted whenever new
audio data is received from the source. This enables other code that is
interested in the raw audio data to directly access it when it becomes
available.

This replaces the old code for the audio meter that was using
calculations in two different places with the new audio meter api.
The source signal will now emit simple levels instead of dB values,
in order to avoid dB conversion and calculation in the source.
The GUI on the other hand now expects simple position values from
the volume meter api with no knowledge about dB calculus either.
That way all code that handles those conversions is in one place,
with the option to easily add new mappings that can be used
everywhere.

Because a vec3 structure can contain a __m128 variable and not the
expected three floats x, y, and z, you must use vec3_set when
setting a value for a vec3 structure to ensure that it uses the proper
intrinsics internally if necessary.

If you look at the previous commits, you'll see I had added
obs_source_draw before.  For custom drawn sources in particular, each
time obs_source_draw was called, it would restart the effect and its
passes for each draw call, which was not optimal.  It should really use
the effect functions for that.  I'll have to add a function to simplify
effect usage.

I also realized that including the color matrix parameters in
obs_source_draw made the function kind of messy to use; instead,
separating the color matrix stuff out to
obs_source_draw_set_color_matrix feels a lot more clean.

On top of that, having the ability to set the position would be nice to
have as well, rather than having to mess with the matrix stuff each
time, so I also added that for the sake of convenience.

obs_source_draw will draw a texture sprite, optionally of a specific
size and/or at a specific position, as well as optionally inverted.  The
texture used will be set to the 'image' parameter of whatever effect is
currently active.

obs_source_draw_set_color_matrix will set the color matrix value if the
drawing requires color matrices.  It will set the 'color_matrix',
'color_range_min', and 'color_range_max' parameters of whatever effect
is currently active.

Overall, these feel much more clean to use than the previous iteration.

This reverts commit ab5a7690.

This function simplifies drawing textures for sources in order to help
reduce boilerplate code.  If a source is a custom drawn source, it will
automatically set up the effect to draw the sprite.  If it's not a
custom drawn source, it will simply draw the sprite as per normal.  If
the source uses a specific color matrix, it will also handle that as
well.

This replaces the call to fmaxf with the equivalent inline comparison
which is a bit faster (at least on linux).

This moves the 'flags' variable from the obs_source_frame structure to
the obs_source structure, and allows user flags to be set for a specific
source.  Having it set on the obs_source_frame structure didn't make
much sense.

OBS_SOURCE_UNBUFFERED makes it so that the source does not buffer its
async video output in order to try to play it on time.  In other words,
frames are played as soon as possible after being received.

Useful when you want a source to play back as quickly as possible
(webcams, certain types of capture devices)

This reverts commit c3f4b0f0.

The obs_source_frame should not need to take flags to do this.  This
shouldn't be a setting associated with the frame, but rather a setting
associated with the source itself.  This was the wrong approach to
solving this particular problem.

If audio timestamps are within the operating system timing threshold,
always use those values directly as a timestamp, and do not apply the
regular jump checks and timing adjustments that normally occur.

This potentially fixes an issue with plugins that use OS timestamps
directly as timestamp values for their audio samples, and bypasses the
timing conversions to system time for the audio line and uses it
directly as the timestamp value.  It prevents those calculations from
potentially affecting the audio timestamp value when OS timestamps are
used.

For example, if the first set of audio samples from the audio source
came in delayed, while the subsequent samples were not delayed, those
first samples could have potentially inadvertently triggered the timing
adjustments, which would affect all subsequent audio samples.

This combines the 'direct' timestamp variance threshold with the maximum
timestamp jump threshold (or rather just removes the max timestamp jump
threshold and uses the timestamp variance threshold for both timestamp
jumps and detecting timestamps).

The reason why this was done was because a timestamp jump could occur at
a higher threshold than the threshold used for detecting OS timestamps
within a certain threshold.  If timestamps got between those two
thresholds it kind of became a weird situation where timestamps could be
sort of 'stuck' back or forward in time more than intended.  Better to
be consistent and use the same threshold for both values.

Add 'flags' member variable to obs_source_frame structure.

The OBS_VIDEO_UNBUFFERED flags causes the video to play back as soon as
it's received (in the next frame playback), causing it to disregard the
timestamp value for the sake of video playback (however, note that the
video timestamp is still used for audio synchronization if audio is
present on the source as well).

This is partly a convenience feature, and partly a necessity for certain
plugins (such as the linux v4l plugin) where timestamp information for
the video frames can sometimes be unreliable.

Due to a small error in the timestamp smoothing code the timestamp of
audio packages that were too early was always set to the next expected
timestamp, even if the difference was bigger than the smoothing threshold.

This would cause obs to simply append all audio data to the buffer even if
the real timestamp was way smaller than the next that was expected.

This should reduce corruption problems with for example the pulseaudio
plugin, which resends data under certain conditions.

obs_source_update_properties should be called by sources when property
values change, e.g. a capture device source would use this when it
detects a new capture device (in case its properties contain a list of
available capture devices or similar)

This Fixes a minor flaw with the API where data had to always be mutable
to be usable by the API.

Functions that do not modify the fundamental underlying data of a
structure should be marked as constant, both for safety and to signify
that the parameter is input only and will not be modified by the
function using it.

Typedef pointers are unsafe.  If you do:
typedef struct bla *bla_t;
then you cannot use it as a constant, such as: const bla_t, because
that constant will be to the pointer itself rather than to the
underlying data.  I admit this was a fundamental mistake that must
be corrected.

All typedefs that were pointer types will now have their pointers
removed from the type itself, and the pointers will be used when they
are actually used as variables/parameters/returns instead.

This does not break ABI though, which is pretty nice.

This helps ensure that an asynchronous video source is played as close
to its framerate as possible, reduces the risk of duplication as
much as possible, and helps to ensure that playback is as smooth as
possible.

This prevents multiple needless calls to obs_source_get_frame and other
functions.  If the texture has already been processed, then just render
it as-is in any subsequent calls to obs_source_video_render.

This is actually unnecessary now that there's a hard limit on the
maximum offset in which audio can be inserted.

This also assumes too much about the audio; it assumes audio is always
on, where as with some devices (such as the elgato) audio is not on
until the stream starts, and when the video has already incremented the
counter.

If the audio didn't start at the 0 timestamp, it would misinterpret it
as a timestamp jump because obs_source::next_audio_ts_min is set to 0 on
creation.  Timestamp starting values should be allowed to start at any
arbitrary value.

Summary:
- Prefix all graphics subsystem names with gs_ or GS_
- Unsquish funciton names (for example _setfloat to _set_float)
- Changed create functions to be more consistent with the rest of the
  API elsewhere.  For exmaple, instead of
  gs_create_texture/gs_texture_destroy, it's now
  gs_texture_create/gs_texture_destroy
- Renamed gs_stencil_op enum to gs_stencil_op_type

From:                            To:
-----------------------------------------------------------
tvertarray                       gs_tvertarray
vb_data                          gs_vb_data
vbdata_create                    gs_vbdata_create
vbdata_destroy                   gs_vbdata_destroy
shader_param                     gs_shader_param
gs_effect                        gs_effect
effect_technique                 gs_effect_technique
effect_pass                      gs_effect_pass
effect_param                     gs_effect_param
texture_t                        gs_texture_t
stagesurf_t                      gs_stagesurf_t
zstencil_t                       gs_zstencil_t
vertbuffer_t                     gs_vertbuffer_t
indexbuffer_t                    gs_indexbuffer_t
samplerstate_t                   gs_samplerstate_t
swapchain_t                      gs_swapchain_t
texrender_t                      gs_texrender_t
shader_t                         gs_shader_t
sparam_t                         gs_sparam_t
effect_t                         gs_effect_t
technique_t                      gs_technique_t
eparam_t                         gs_eparam_t
device_t                         gs_device_t
graphics_t                       graphics_t
shader_param_type                gs_shader_param_type
SHADER_PARAM_UNKNOWN             GS_SHADER_PARAM_UNKNOWN
SHADER_PARAM_BOOL                GS_SHADER_PARAM_BOOL
SHADER_PARAM_FLOAT               GS_SHADER_PARAM_FLOAT
SHADER_PARAM_INT                 GS_SHADER_PARAM_INT
SHADER_PARAM_STRING              GS_SHADER_PARAM_STRING
SHADER_PARAM_VEC2                GS_SHADER_PARAM_VEC2
SHADER_PARAM_VEC3                GS_SHADER_PARAM_VEC3
SHADER_PARAM_VEC4                GS_SHADER_PARAM_VEC4
SHADER_PARAM_MATRIX4X4           GS_SHADER_PARAM_MATRIX4X4
SHADER_PARAM_TEXTURE             GS_SHADER_PARAM_TEXTURE
shader_param_info                gs_shader_param_info
shader_type                      gs_shader_type
SHADER_VERTEX                    GS_SHADER_VERTEX
SHADER_PIXEL                     GS_SHADER_PIXEL
shader_destroy                   gs_shader_destroy
shader_numparams                 gs_shader_get_num_params
shader_getparambyidx             gs_shader_get_param_by_idx
shader_getparambyname            gs_shader_get_param_by_name
shader_getviewprojmatrix         gs_shader_get_viewproj_matrix
shader_getworldmatrix            gs_shader_get_world_matrix
shader_getparaminfo              gs_shader_get_param_info
shader_setbool                   gs_shader_set_bool
shader_setfloat                  gs_shader_set_float
shader_setint                    gs_shader_set_int
shader_setmatrix3                gs_shader_setmatrix3
shader_setmatrix4                gs_shader_set_matrix4
shader_setvec2                   gs_shader_set_vec2
shader_setvec3                   gs_shader_set_vec3
shader_setvec4                   gs_shader_set_vec4
shader_settexture                gs_shader_set_texture
shader_setval                    gs_shader_set_val
shader_setdefault                gs_shader_set_default
effect_property_type             gs_effect_property_type
EFFECT_NONE                      GS_EFFECT_NONE
EFFECT_BOOL                      GS_EFFECT_BOOL
EFFECT_FLOAT                     GS_EFFECT_FLOAT
EFFECT_COLOR                     GS_EFFECT_COLOR
EFFECT_TEXTURE                   GS_EFFECT_TEXTURE
effect_param_info                gs_effect_param_info
effect_destroy                   gs_effect_destroy
effect_gettechnique              gs_effect_get_technique
technique_begin                  gs_technique_begin
technique_end                    gs_technique_end
technique_beginpass              gs_technique_begin_pass
technique_beginpassbyname        gs_technique_begin_pass_by_name
technique_endpass                gs_technique_end_pass
effect_numparams                 gs_effect_get_num_params
effect_getparambyidx             gs_effect_get_param_by_idx
effect_getparambyname            gs_effect_get_param_by_name
effect_updateparams              gs_effect_update_params
effect_getviewprojmatrix         gs_effect_get_viewproj_matrix
effect_getworldmatrix            gs_effect_get_world_matrix
effect_getparaminfo              gs_effect_get_param_info
effect_setbool                   gs_effect_set_bool
effect_setfloat                  gs_effect_set_float
effect_setint                    gs_effect_set_int
effect_setmatrix4                gs_effect_set_matrix4
effect_setvec2                   gs_effect_set_vec2
effect_setvec3                   gs_effect_set_vec3
effect_setvec4                   gs_effect_set_vec4
effect_settexture                gs_effect_set_texture
effect_setval                    gs_effect_set_val
effect_setdefault                gs_effect_set_default
texrender_create                 gs_texrender_create
texrender_destroy                gs_texrender_destroy
texrender_begin                  gs_texrender_begin
texrender_end                    gs_texrender_end
texrender_reset                  gs_texrender_reset
texrender_gettexture             gs_texrender_get_texture
GS_BUILDMIPMAPS                  GS_BUILD_MIPMAPS
GS_RENDERTARGET                  GS_RENDER_TARGET
gs_device_name                   gs_get_device_name
gs_device_type                   gs_get_device_type
gs_entercontext                  gs_enter_context
gs_leavecontext                  gs_leave_context
gs_getcontext                    gs_get_context
gs_renderstart                   gs_render_start
gs_renderstop                    gs_render_stop
gs_rendersave                    gs_render_save
gs_getinput                      gs_get_input
gs_geteffect                     gs_get_effect
gs_create_effect_from_file       gs_effect_create_from_file
gs_create_effect                 gs_effect_create
gs_create_vertexshader_from_file gs_vertexshader_create_from_file
gs_create_pixelshader_from_file  gs_pixelshader_create_from_file
gs_create_texture_from_file      gs_texture_create_from_file
gs_resetviewport                 gs_reset_viewport
gs_set2dmode                     gs_set_2d_mode
gs_set3dmode                     gs_set_3d_mode
gs_create_swapchain              gs_swapchain_create
gs_getsize                       gs_get_size
gs_getwidth                      gs_get_width
gs_getheight                     gs_get_height
gs_create_texture                gs_texture_create
gs_create_cubetexture            gs_cubetexture_create
gs_create_volumetexture          gs_voltexture_create
gs_create_zstencil               gs_zstencil_create
gs_create_stagesurface           gs_stagesurface_create
gs_create_samplerstate           gs_samplerstate_create
gs_create_vertexshader           gs_vertexshader_create
gs_create_pixelshader            gs_pixelshader_create
gs_create_vertexbuffer           gs_vertexbuffer_create
gs_create_indexbuffer            gs_indexbuffer_create
gs_gettexturetype                gs_get_texture_type
gs_load_defaultsamplerstate      gs_load_default_samplerstate
gs_getvertexshader               gs_get_vertex_shader
gs_getpixelshader                gs_get_pixel_shader
gs_getrendertarget               gs_get_render_target
gs_getzstenciltarget             gs_get_zstencil_target
gs_setrendertarget               gs_set_render_target
gs_setcuberendertarget           gs_set_cube_render_target
gs_beginscene                    gs_begin_scene
gs_draw                          gs_draw
gs_endscene                      gs_end_scene
gs_setcullmode                   gs_set_cull_mode
gs_getcullmode                   gs_get_cull_mode
gs_enable_depthtest              gs_enable_depth_test
gs_enable_stenciltest            gs_enable_stencil_test
gs_enable_stencilwrite           gs_enable_stencil_write
gs_blendfunction                 gs_blend_function
gs_depthfunction                 gs_depth_function
gs_stencilfunction               gs_stencil_function
gs_stencilop                     gs_stencil_op
gs_setviewport                   gs_set_viewport
gs_getviewport                   gs_get_viewport
gs_setscissorrect                gs_set_scissor_rect
gs_create_texture_from_iosurface gs_texture_create_from_iosurface
gs_create_gdi_texture            gs_texture_create_gdi
gs_is_compressed_format          gs_is_compressed_format
gs_num_total_levels              gs_get_total_levels
texture_setimage                 gs_texture_set_image
cubetexture_setimage             gs_cubetexture_set_image
swapchain_destroy                gs_swapchain_destroy
texture_destroy                  gs_texture_destroy
texture_getwidth                 gs_texture_get_width
texture_getheight                gs_texture_get_height
texture_getcolorformat           gs_texture_get_color_format
texture_map                      gs_texture_map
texture_unmap                    gs_texture_unmap
texture_isrect                   gs_texture_is_rect
texture_getobj                   gs_texture_get_obj
cubetexture_destroy              gs_cubetexture_destroy
cubetexture_getsize              gs_cubetexture_get_size
cubetexture_getcolorformat       gs_cubetexture_get_color_format
volumetexture_destroy            gs_voltexture_destroy
volumetexture_getwidth           gs_voltexture_get_width
volumetexture_getheight          gs_voltexture_get_height
volumetexture_getdepth           gs_voltexture_getdepth
volumetexture_getcolorformat     gs_voltexture_get_color_format
stagesurface_destroy             gs_stagesurface_destroy
stagesurface_getwidth            gs_stagesurface_get_width
stagesurface_getheight           gs_stagesurface_get_height
stagesurface_getcolorformat      gs_stagesurface_get_color_format
stagesurface_map                 gs_stagesurface_map
stagesurface_unmap               gs_stagesurface_unmap
zstencil_destroy                 gs_zstencil_destroy
samplerstate_destroy             gs_samplerstate_destroy
vertexbuffer_destroy             gs_vertexbuffer_destroy
vertexbuffer_flush               gs_vertexbuffer_flush
vertexbuffer_getdata             gs_vertexbuffer_get_data
indexbuffer_destroy              gs_indexbuffer_destroy
indexbuffer_flush                gs_indexbuffer_flush
indexbuffer_getdata              gs_indexbuffer_get_data
indexbuffer_numindices           gs_indexbuffer_get_num_indices
indexbuffer_gettype              gs_indexbuffer_get_type
texture_rebind_iosurface         gs_texture_rebind_iosurface
texture_get_dc                   gs_texture_get_dc
texture_release_dc               gs_texture_release_dc

Renamed:                  To:
-------------------------------------------------
calldata_getdata          calldata_get_data
calldata_getint           calldata_get_int
calldata_getfloat         calldata_get_float
calldata_getbool          calldata_get_bool
calldata_getptr           calldata_get_ptr
calldata_getstring        calldata_get_string
calldata_setdata          calldata_set_data
calldata_setint           calldata_set_int
calldata_setfloat         calldata_set_float
calldata_setbool          calldata_set_bool
calldata_setptr           calldata_set_ptr
calldata_setstring        calldata_set_string

Renamed:                        To:
-----------------------------------------------------------
audio_output_blocksize          audio_output_get_block_size
audio_output_planes             audio_output_get_planes
audio_output_channels           audio_output_get_channels
audio_output_samplerate         audio_output_get_sample_rate
audio_output_getinfo            audio_output_get_info
audio_output_createline         audio_output_create_line
video_output_getinfo            video_output_get_info
video_gettime                   video_output_get_time
video_getframetime              video_output_get_frame_time
video_output_width              video_output_get_width
video_output_height             video_output_get_height
video_output_framerate          video_output_get_frame_rate
video_output_num_skipped_frames video_output_get_skipped_frames
video_output_total_frames       video_output_get_total_frames

Renamed:                       To:
-------------------------------------------------------
obs_source_info::defaults       obs_source_info::get_defaults
obs_source_info::properties     obs_source_info::get_properties
obs_output_info::defaults       obs_output_info::get_defaults
obs_output_info::properties     obs_output_info::get_properties
obs_output_info::total_bytes    obs_output_info::get_total_bytes
obs_output_info::dropped_frames obs_output_info::get_dropped_frames
obs_encoder_info::defaults      obs_encoder_info::get_defaults
obs_encoder_info::properties    obs_encoder_info::get_properties
obs_encoder_info::extra_data    obs_encoder_info::get_extra_data
obs_encoder_info::sei_data      obs_encoder_info::get_sei_data
obs_encoder_info::audio_info    obs_encoder_info::get_audio_info
obs_encoder_info::video_info    obs_encoder_info::get_video_fino
obs_service_info::defaults      obs_service_info::get_defaults
obs_service_info::properties    obs_service_info::get_properties