Log Message:
Update to 1.3.1:

libvorbis 1.3.1 (2010-02-26) -- "Xiph.Org libVorbis I 20100325 \ 
(Everywhere)"

 * tweak + minor arithmetic fix in floor1 fit
 * revert noise norm to conservative 1.2.3 behavior pending
   more listening testing

libvorbis 1.3.0 (2010-02-25) -- unreleased staging snapshot

 * Optimized surround support for 5.1 encoding at 44.1/48kHz
 * Added encoder control call to disable channel coupling
 * Correct an overflow bug in very low-bitrate encoding on 32 bit
   machines that caused inflated bitrates
 * Numerous API hardening, leak and build fixes
 * Correct bug in 22kHz compand setup that could cause a crash
 * Correct bug in 16kHz codebooks that could cause unstable pure
   tones at high bitrates