Allocate thread descriptor from pool in portaudio callback

Ignore-this: e045e4c6cdfbad9470322ebde85add66

darcs-hash:20100420140145-1e3d8-365cf3dec7c704283c039c0df6ab7becf37dcf1c
Removed obsolete files

darcs-hash:20100419212358-58252-0c0d66bf68bba50e43a4d24d6556218aefecd81a