This adds obfuscation functions primarily for use with GetProcAddress.
This takes an obfuscated string and uses a simple integer key to
de-obfuscate it to the intended function name string, which is then
loaded dynamically using GetProcAddress.

This is typically only used with functions such as OpenProcess,
SetWindowsHookEx, and the like, which can often be misinterpreted the
wrong way by security programs if those strings are found within the
strings segment of a scanned executable.

When getting the class/title/exe of a particular window handle in the
build_window_strings function, always set the class/title/exe pointers
to null to prevent any potential references to invalid values if any of
them do not happen to be set for whatever reason.

On certain GPUs, if you don't flush and the window is minimized it can
endlessly accumulate memory due to what I'm assuming are driver design
flaws (though I can't know for sure).  The flush seems to prevent this
from happening, at least from my tests.  It would be nice if this
weren't necessary.

Volume meter improvements

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.

This adds the conversion function used by the old obs based on a
logarithmic scale.

This adds a new fader type that implements a position/dB mapping
as specified in IEC 60-268-18.

This adds a volume meter object to libobs that can be used by the GUI
or plugins to convert the raw audio level data from sources to values
that can easily be used to display the audio data.
The volume meter object will use the same mapping functions as the
fader object to map dB levels to a scale.

libobs: Use FFmpeg for image loading by default

Add more details installation/compilation instructions for
Redhat-based distros, debian-based distros, Arch Linux, Gentoo, and
OpenSUSE distros

Fix incomplete Debian installation instructions, and separate out
instructions and package requirements that were specific to Debian-based
distros.  Most of the instructions in the file were previously specific
only to Debian.  Also added some brief instructions for an easy and
minimal FFmpeg installation.

In older versions of visual studio 2013 microsoft's WORTHLESS C compiler
has a bug where it will, almost at random, not be able to handle having
variables declared in the middle of a function and give the warning:
"illegal use of this type as an expression".  It was fixed in recent
VS2013 updates, but I'm not about to force everyone to update to it.

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.

The macro INFINITY apparently will trigger a warning with microsoft's
compiler despite being a C standard library macro.

This adds functions for piping a command line program's stdin or stdout.
Note however that this is unidirectional only.

This will be especially useful later on when implementing MP4 output,
because MP4 output has to be piped to prevent unexpected program
termination from corrupting the file.

Add advanced audio controls

There's a little too much junk in the CONTRIBUTING file.  I feel like
it's unnecessary to say some of the things that were being said in
there.  It really needs to be to the point

This replaces the code for volume control with a newer version that
uses the new fader implementation in order to control the fader/slider
position and source volume.
The volume label will now indicate the gain in dB instead of percent,
mainly because it looks cool and is easy to do.
Due to libobs saving the multiplier option for the source instead of
the slider/fader positon, existing volume levels will (mostly) stay
the same with only the slider beeing at a different position.
This is of course within the resolution of the slider (100 steps).

This adds a new library of audio control functions mainly for the use in
GUIS. For now it includes an implementation of a software fader that can
be attached to sources in order to easily control the volume.
The fader can translate between fader-position, volume in dB and
multiplier with a configurable mapping function.
Currently only a cubic mapping (mul = fader_pos ^ 3) is included, but
different mappings can easily be added.

Due to libobs saving/restoring the source volume from the multiplier,
the volume levels for existing source will stay the same, and live
changing of the mapping will work without changing the source volume.

This function greatly simplifies the use of effects by making it so you
can call this function in a simple loop.  This reduces boilerplate and
makes drawing with effects much easier.  The gs_effect_loop function
will now automatically handle all the functions required to do drawing.

---------------------
Before:

gs_technique_t *technique = gs_effect_get_technique("technique");

size_t passes = gs_technique_begin(technique);
for (size_t pass = 0; pass < passes; pass++) {
	gs_technique_begin_pass(technique, pass);

	[draw]

	gs_technique_end_pass(technique);
}
gs_technique_end(technique);

---------------------
After:

while (gs_effect_loop(effect, "technique")) {
	[draw]
}

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.

linux-xshm: Allow capturing from a different X server

This adds a check to the screen enumeration in order to handle missing
screens by adding them to the list but disabling them.

This adds a property to the source properties which lets the user
specify the X server to capture from. Since this is probably something
thats only useful under certain circumstances it is implemented as
an advanced setting which is only shown when the corresponding option
for advanced settings is checked.

This moves the code to start/stop the capture to respectively named
function in order to clean up the update function.
This means that the capture is stopped/started whenever the settings are
changed. While this increases overhead for some settings, this will also
enable future settings that require a full restart of capture process.

This removes the entering/leaving of the graphics context from this
function and requires the calling code to make sure the context is
present.

This adds the screen id from the source properties to the source
struct and changes the geometry function to use that value instead
of requiring the settings object of the source.

This adds a macro to automatically prepend the plugin name to debug
statements like it is done in other plugins.

This adds documentation to the source struct and moves one bool to the
end to avoid a hole due to alignment.

On windows, carriage return characters are used along with line feed
characters. When the carriage return is used, it's rendered as a space.
This removes carriage returns from strings before rendering them via
freetype.

Allows a blank stream key to be used for RTMP streams.

libobs: Replace fmaxf with inline comparison.

Doing this in the expression will cause it to execute the function every
time the expression is evaluated, which is needless cycles wasted.
Instead, call wcslen before the loops begin.

If FFmpeg's experimental aac encoder is used, this changes the cutoff
frequency to better values in order to try to help make up for the
inherent lack of encoder quality a bit.  If FFmpeg is compiled to use
another encoder by default, these settings will not be applied.