RtAudio (<https://caml.music.mcgill.ca/~gary/rtaudio/>,
<https://github.com/thestk/rtaudio>) library version 6.0.1 (2023-08-01).
The following changes have been made:
 *  OpenMPT modifications are marked with "// OpenMPT".
 *  For building, premake is used to generate Visual Studio project files.
    See ../build/premake/ for details.
