#93 Add portaudio support
portaudio (http://www.portaudio.com/) is a portable audio I/O layer. It doesn't currently support everything that we do (in particular, no Sun audio, and ALSA is under development), but it does support input, in particular, on a wider range of platforms than we currently have (including Windows and Mac OS X). Development is currently diffuse (the "current" release 18, as seen in Debian, is way out of date, and the new release 19 seems not quite to have stabilised, though it's advertised as stable) but I don't think writing another format module will take long, and it might help them if lots of SoX users are suddenly flooding them! Naturally, it already also helps us, and might well allow us at least to retire the OSS code, as portaudio if nothing else has solid OSS support.
