Allows Lua/Python scripting support.

Intended to replace libff as the media playback library.  Intended to
use less threads and be more extensible.  It was nearly impossible to
modify libff without bursting a vein.

Used by the update module on windows.

Manually merging/squashing from: https://github.com/szatmary/libcaption

This allows plugins to update and cache data files from a remote source.

Here are the steps that occur when the API initiates an update check:

1.) It checks to see if the local files are greater than the cached
    files.  If the local version is newer (for whatever reason), it
    replaces the cached version(s) with the local version.

2.) A packages.json file is downloaded from the specified URL.  That
    packages.json file contains a version number and a list of files to
    be updated.

3.) If the downloaded package version is greater than the cached
    version, executes step 4-5 on each file.

4.) Checks the version for the file to update in packages.json, and if
    the version is greater than the cached version, proceeds to step 5,
    otherwise repeat step 4-5 for other files.

5.) Calls the callback given to the update function (if any) with the
    file information (file name, buffer, etc), and if the callback
    returns true, allows the cached file to be updated and replaced,
    otherwise goes back to step 4-6 for the rest of the files.

NOTE: Files are never modified directly.  All file saving/modification
is performed in a temporary directory, and then files are moved to their
destination.  This should eliminate any possibility of file corruption
(or at least dramatically reduce the possibility).

This library wraps the ffmpeg library and adds some utility
functions and types.

mingw-w64 has its own pthreads library

Originally I made the "win_pipe" stuff for named pipes on windows but it
was argued that it should be available to all modules and
programs/libraries that the modules might communicate with.

It cannot really be put in to libobs due to the fact that there would
hypothetically be things unrelated to libobs that might want to use it,
so I felt the best option was just to create a simple static library
specific for interprocess communication.

Non-windows versions of these functions are still yet to be implemented.

CMake now works on all platforms