Change #6685: Replace Win32 music driver with one not depending on MCI
MCI MIDI is poorly supported on newer versions of Windows and can cause large
delays at the beginning of tracks.
The new driver is based on a from-scratch reader for Standard MIDI Files. This
should be re-usable in other music drivers too, and can allow for finer control
of playback in general.
It also provides a better framework for reading MIDI data from other formats
than just SMF.
(cherry picked from commit
b902e01e10b193749bd4367a6042ceb3cf3a7d54)
# Conflicts:
# src/music/win32_m.cpp