IDirectMusicPerformanceImpl (as the first inherits from the second)
- implement many Loader, AudioPath and Performance8 stubs - fix the
  class factory
- more debug traces
- for now IDirectMusicLoader8::LoadObjectFromFile always returns not
  supported format
- fix the IDirectMusicPerformance8::Init (many crashes)
- implementation of IDirectMusicPerformance8InitAudio