* configure.ac.in: libvorbis depends on libogg.
* include/vlc_threads.h: changed the different threads priorities to optimize
   audio and video quality as well as responsiveness.
* modules/audio_output/waveout.c modules/audio_output/directx.c: waveout and
   directx will now use the float32 format if available. Various tweaks for
   better performance.