Audio Capturing Support Landed This Week In SDL2

In addition to the relative mouse mode for Wayland support landing within the SDL2 code-base, the ongoing work around audio capturing was also committed to mainline.

The work led by Ryan "Icculus" Gordon provides for audio capturing via the SDL2 library and support for unified audio capturing on all major platforms. Simple DirectMedia Layer is the library commonly used by games and other applications that provides a nice abstraction layer between platforms/hardware with audio capturing being the latest feature addition.

The merge happened with this commit. All of these recent SDL2 changes will end up in SDL v2.0.5 that hopefully won't be dragged out too much further until release time.