implement alsa capability

[ekilfoil]

create audio streams using alsa

[ekilfoil]

modifying this to major. this will not make it into 1.0

[ekilfoil]

implementing alsa will probably require writing an audio muxer internally. I'm not sure I understand alsa access enough to know what is and is not required and documentation is scarce.

The way I understand it (which could very well be wrong) is that alsa requires a single stream. The dmix interface (i think) is not suitable for our purposes since we have an undefined number of streams possible. I *think* we have to mux these streams internally before sending them to ALSA.

Of course, this could be completely wrong. If someone that knows how to use the alsa lib better can help, that would be great. Until then, this will require internal muxing.

[ekilfoil]

done in r482 (without a mixer!)