o	finish improvements in recording support
	- find a way to select the recording buffer
	- support for the FX output register control
	Both will probably be implemented with a new mixer & dsp ioctl
o	implement /dev/sequencer
o	put support for midi, mixer in different modules (maybe)
o	get digital ouput and A3-C sound working properly
o	add mixer ioctl to query and modify active voices parameters
	(the objective is to create a hook for an advanced mixer/effects
	manager).
	add a similar dsp ioctl but that only affects the voice (mono or
	stereo) associated with the /dev/dsp file descriptor.
	Things to control:
	- routing. FXRT_CHANNELx
	- ...
o	provide a way to accuruatly synchronize a group of voices. This seems
	essential for proper hardware voice mixing.
