Relaxed constraints on audio buffering to allow use with less flexible
sound-cards. Code now permits only simple double-buffering (2 frags)
and bugger (frag) sizes of only 4096. The drivers for some modern PCI
cards don't like delivering the larger (8192 byte) frags and 8 buffers
demanded by the original code.
Added code to run audio capture as a X/Open real-time thread rather
than as a seperate ordinary process. This should obviate the need
for so many / such large frags.
