Stage 2 (before final 0.2.0):

* timer interface (done)
* sequencer
  - only external MIDI support

Stage 3:

* sequencer
  - add internal synthesizer interface

Stage 4:

* sequencer
  - add MIDI emulation for internal synthesizer

General:

* extend documentation for programmers (driver side)
* extend documentation for users
* detection for OAK Mozart soundcards
* detection for Yamaha OPL3-SA[2,3] soundcards
* code for multiple playback PCM devices for GF1 chip (GUS cards)
* setup CVS
