in the playback buffer and waiting until there's enough space anyway.
- use -pthread instead of -lpthread for pthreads linkage
- don't even try to use the "real time sample counter" on *BSD, since
it's not that same as with Sun audio.
- use the audio(4) interface to the mixer "master" volume control
- actually mute the audio when output volume is '0'
- set the audio(4) blocksize to match size of chunks to be written
- provide *BSD equivilents to some Sun functionality
