RtMidi cross-platform MIDI classes
version 4.0.0 from https://github.com/thestk/rtmidi/
Files not used by OpenMPT (config/, doc/, msw/, tests/, build systems, C API)
have been removed from this folder. No further local changes have been made.
License.txt has been extracted from the readme for OpenMPT's license package.

For building, premake is used to generate Visual Studio project files.
See ../build/premake/ for details.