(Non-compiling commit: windowless-context branch)

glFlush is somewhat implementation-specific; on OSX for example, it is
additionally used to draw to a view.  However, we're already using the
Objective-C function flushBuffer, which apparently calls glFlush
internally anyway to draw to views.  That means that we're superfluously
calling glFlush most of the time if there's an active swap chain.  So
instead, only call glFlush when there are no active swap chains on OSX.

This allows the ability to separate the blend states of color and alpha.

The default blend state has also changed so that alpha is always added
together to ensure that the destination image always gets an alpha value
that is actually usable after the operation (for render targets).

Old default state:
  color source: GS_BLEND_SRCALPHA, color dest: GS_BLEND_INVSRCALPHA
  alpha source: GS_BLEND_SRCALPHA, alpha dest: GS_BLEND_INVSRCALPHA

New default state:
  color source: GS_BLEND_SRCALPHA, color dest: GS_BLEND_INVSRCALPHA
  alpha source: GS_BLEND_ONE,      alpha dest: GS_BLEND_ONE

If a render target was switched from one to another and then back
consecutively, the texture would not get reattached at the last point
due to the fact that the cur_render_target variable of the FBO storage
structure would already be set to that texture, and then it would never
get reattached because it thought it was already using that render
target.

So to fix this, any time a render target legitimately changes from one
to another, it sets the cur_render_target and cur_zstencil_buffer
variables of the FBO structure to null.

When render targets are used, they output to the render target inverted
due to the way that opengl works.  This fixes that issue by inverting
the projection matrix so that it renders the image upside down and
inverting the front face from counterclockwise to clockwise.

The anisotropy message isn't particularly useful for users.

The glDebugMessageCallback function will set a callback that will relay
all messages coming from the driver (on supported drivers at least).
For nvidia, sometimes there are a lot of irrelevant messages, which is
nice depending on the type of application you're writing.

I actually at first thought these messages were important, but it turns
out that they're almost always irrelevant and not actually warnings.
Most of the messages at a certain type/severity are mostly for debugging
purposes or minor hints about how to maximize performance, so
unfortunately there ends up being a lot of pointless spam in the debug
output.

The particular performance messages are related to optimizations you can
get via multithreading, and are optimizations you would expect for games
more than for this type of application.  They don't really apply for our
use cases most of the time.

High severity messages however are not omitted regardless of message
type.

These messages can be enabled again by simply defining the
SHOW_ALL_GL_MESSAGES macro.

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 replaces the ARB_separate_shader_objects extension with traditional
linked shaders.  I was able to get the existing system to use linked
shaders without having to change any libobs graphics API.

This essentially creates a linked list of shader programs with
references to the shaders they link.  Before draw, it searches that
linked list for a particular pixel/vertex shader pair, and the linked
program associated with it.  If no matching program exists, it creates
the program.

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

Changed API functions:
libobs: obs_reset_video

Before, video initialization returned a boolean, but "failed" is too
little information, if it fails due to lack of device capabilities or
bad video device parameters, the front-end needs to know that.

The OBS Basic UI has also been updated to reflect this API change.

This allows a programatic way of determining the type of graphics module
currently active.

This returns the name of the device, "Direct3D 11" or "OpenGL"
respectively.

NOTE: In texture_setimage, I had to move variables to the top of the
scope because microsoft's C compiler will give the legacy C90 error of:
'illegal use of this type as an expression'.

To sum it up, microsoft's C compiler is still utter garbage.

...I'm actually concerned that I went a bit overkill trying to prevent
backwards compatibility issues with this abstraction design, because
this is a large number of files that have to be modified just to add a
single graphics subsystem export.  Someone's going to strangle me, and
when you know that someone might strangle you, that means that you did
something wrong.  We'll have to look in to simplifying this in the
future without killing backward compatibility safety.

These functions were mostly related to being able to set true fullscreen
mode -- however, this has no place for our purposes, and these functions
were just sitting empty and unused, so they should be removed.

Besides, fullscreen mode only applies to the windows operating system.

4x4 matrices aren't as optimal, but are much more sensible to handle
when you want to do more advanced stuff like scaling, skewing, or
inversion.

My prior code was incorrect;  I mixed up the two parameters, the
GL_TEXTURE_SWIZZLE_* parameter specifies the target channel, and the
value itself specifies the source channel.,  If that makes sense.

Avoids problems if swizzles are used elsewhere (like in the newer X11
plugins)

Was wrong to use the swizzle -- it was an incorrect assumption on my
part that this could work in the first place (despite working on
windows)

On some operating systems, with specific drivers it seems that BGR/BGRA
isn't properly treated as such in certain cases.  This fix will
hopefully force the formats to be treated as BGR/BGRA when actually
rendering, which should get around the implementation-specific issue.

 - Changed glMapBuffer to glMapBufferRange to allow invalidation.  Using
   just glMapBuffer alone was causing some unacceptable stalls.

 - Changed dynamic buffers from GL_DYNAMIC_WRITE to GL_STREAM_WRITE
   because I had misunderstood the OpenGL specification

 - Added _OPENGL and _D3D11 builtin preprocessor macros to effects to
   allow special processing if needed

 - Added fmod support to shaders (NOTE: D3D and GL do not function
   identically with negative numbers when using this.  Positive numbers
   however function identically)

 - Created a planar conversion shader that converts from packed YUV to
   planar 420 right on the GPU without any CPU processing.  Reduces
   required GPU download size to approximately 37.5% of its normal rate
   as well.  GPU usage down by 10 entire percentage points despite the
   extra required pass.

There were a *lot* of warnings, managed to remove most of them.

Also, put warning flags before C_FLAGS and CXX_FLAGS, rather than after,
as -Wall -Wextra was overwriting flags that came before it.

Reduces needless code repetition and still allows for proper memory
alignment.  Cleans up the code a bit.

This trick uses FBOs to allow for copying textures without the need for
special texture copy functions.

- Add planar audio support.  FFmpeg and libav use planar audio for many
  encoders, so it was somewhat necessary to add support in libobs
  itself.

- Improve/adjust FFmpeg test output plugin.  The exports were somewhat
  messed up (making me rethink how exports should be done).  Not yet
  functional; it handles video properly, but it still does not handle
  audio properly.

- Improve planar video code.  The planar video code was not properly
  accounting for row sizes for each plane.  Specifying row sizes for
  each plane has now been added.  This will also make it more compatible
  with FFmpeg/libav.

- Fixed a bug where callbacks wouldn't create properly in audio-io and
  video-io code.

- Implement 'blogva' function to allow for va_list usage with libobs
  logging.