The decay rate of the audio meters can now be selected in the audio
settings.  The values are:

- "Fast"   (OBS default, 40 dB / 1.7s)
- "Medium" (Type I PPM,  20 dB / 1.7s)
- "Slow"   (Type II PPM, 24 dB / 2.8s)

Closes jp9000/obs-studio#1143

With the "instant-replay.lua" script, it would only play the last replay
buffer saved, meaning the user would have to save a replay with the
replay buffer hotkey, and then press the "Play Last Replay" hotkey to
play the last replay buffer.

Instead, combine the two and make the script save the replay
automatically first, and then play it back as soon as it's available.
This makes it actually qualify as an "instant replay" script, as its
name implies.

A script that plays back the last replay buffer in the specified media
source.

These functions aren't particularly useful in C/C++, but these functions
are necessary to allow creating/destroying a calldata_t object via
script.

Lua uses 1-based index on table insertions, and lua_newtable has a bit
better performance than lua_createtable if initializing tables with an
unknown item count.

Allows getting the path of the last replay buffer saved via the
procedure handler of the FFmpeg muxer output.

Closes jp9000/obs-studio#1158

Closes jp9000/obs-studio#1150

Closes jp9000/obs-studio#1157

This improves detection by performing an actual check on encoder
capability directly with the NVENC/CUDA libraries.

If a filter's implementation (its plugin for example) no longer exists,
it would cause the source to stop rendering if that filter was present
on the source.  Instead, just bypass the filter to ensure that the
source continues to render.

Prevents calling memset on mixes that aren't currently active.

The memset in custom_audio_render() did not clear all audio buffers when
the number of output channels was less then 8.  This caused wrong audio
output on mixes that did not get cleared.

Closes jp9000/obs-studio#1123

Fixed a Typo on the 34th line, and added to the 35th so that the Syntax
matches that of the rest of the file.

Closes jp9000/obs-studio#1146

libobs: Fix log message

CMake: Fix FindSwigDeps search path

UI: Fix tab bars for docked widgets in Dark theme

deps/obs-scripting: Various scripting fixes

Uses the 'install' command in cmake to install scripting modules/files
(such as _obspython.so, obslua.so, and obspython.py), and changes the
install location of those files on all operating systems.  If using a
non-unix structure install, those files will be installed in
data/obs-scripting/[32bit/64bit], otherwise with unix structure installs
those files will be installed to [/usr/local/lib]/obs-scripting.

Before the new volume meters were implemented, the meter would flash red
if the audio was clipping.  This functionality was removed when the
meters were changed, whether intentionally or unintentionally, and this
patch puts that functionality back in.  If clipping occurs, the meters
will be fully colored with the foregroundErrorColor value while the
clipping is occurring.

Adds a source which tests whether audio buffering affects audio sync.
This sync test cycles through 7 audio/video frequencies at 250
millisecond intervals, and via a hotkey, will artificially move audio
time back by one second (and the audio cycle back by 4 frequencies).
This will artificially increase audio buffering by approximately 750
milliseconds.

Results from this test as of this writing: this test proves that dynamic
audio buffering does not affect sync.

Refines warning message to make it clear for the end-user.

Module may fail to load by different reasons.

This reverts commit 94b59822.

Reverting this commit because it had some negative side effects, such as
adding 500 milliseconds to the startup time.  NVENC detection should
really be done through its proper API, and not via creating an encoder
on startup.

Prevents a potential memory leak if data was previously allocated in the
frame.