sceAudioOutputPannedBlocking() returns # samples.

Or seems to, anyway.  This fixes things like:

stdout: SCREAM: Lib wave didn't take all of our last submit (took 0 of
2048)!
Allow sceAudioChReserve() to choose a channel.

Not just only -1.
Track Atrac as a map and associate data.
Return saner fake sample sizes in atrac.
Keep track of the atrac buffer size and return it.
More correctly lie that atrac decoding finished.
Merge pull request #562 from unknownbrackets/audio-minor

Audio / Atrac tweaks (needs more testing)