

make sure |fft[0]| can't be negative (eits todB_nn)

svn path=/trunk/vorbis/; revision=1355

nicolaichuk/vorbis,ShiftMediaProject/vorbis,ShiftMediaProject/vorbis,erikd/vorbis,emscripten-ports/Vorbis,ShiftMediaProject/vorbis,nicolaichuk/vorbis,ShiftMediaProject/vorbis,emscripten-ports/Vorbis,felipebetancur/vorbis,youfearm3/vorbis,mwgoldsmith/vorbis,erikd/vorbis,erikd/vorbis,eidy/vorbis,eidy/vorbis,felipebetancur/vorbis,felipebetancur/vorbis,ksophocleous/vorbis,emscripten-ports/Vorbis,ShiftMediaProject/vorbis,mwgoldsmith/vorbis,mwgoldsmith/vorbis,youfearm3/vorbis,youfearm3/vorbis,ksophocleous/vorbis,eidy/vorbis,youfearm3/vorbis,nicolaichuk/vorbis,erikd/vorbis,felipebetancur/vorbis,ksophocleous/vorbis,mwgoldsmith/vorbis,emscripten-ports/Vorbis,eidy/vorbis,nicolaichuk/vorbis,ShiftMediaProject/vorbis,ksophocleous/vorbis