ffmpeg: Don't include colorspace.h

The header is private, and ffmpeg.c doesn't use it
for anything.

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
mjpeg_decode_dc: check code before using it in get_xbits()

Fixes undefined behavior

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
4xm: check for invalid zero ac coeffs

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
4xm: Dont ignore dc run errors

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
get_xbits: assert validity of the number of bits

similar is already done in the other get_bits() functions

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