WinMM loads mapper drivers too early

MIDI Mapper driver expects other MIDI device drivers already loaded at DRV_OPEN (MIDIMAP_drvOpen), it calls midiOutGetNumDevs to get MIDI output count.

WinMM enumerates Drivers32 registry key and loads each driver in a loop. MIDI Mapper driver is being loaded before actual MIDI device drivers, so the mapper could not initialize correctly and thus could not play the music.