[PATCH] _ilog() method
_ilog doesn't properly return 0 when a negative number is passed. See: http://lists.xiph.org/pipermail/theora-dev/2007-March/003202.html
_ilog doesn't properly return 0 when a negative number is passed. See: http://lists.xiph.org/pipermail/theora-dev/2007-March/003202.html