fft: add missing const.

This table was the largest object in FFmpeg's .data,
and really should be in .rodata.

Signed-off-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>
oggdec: fix invalid free on error

The read_packet callback passes a pointer to a stack-allocated AVPacket.
Attempting to free it with av_free() makes no sense.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>