avfilter/vf_noise: use per component rand_shift

This allows using different shifts per plane

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avfilter/vf_noise: Use a separate seed for each plane

This should reduce the correlation between planes

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avformat/id3v2: silence a warning when CONFIG_ZLIB is unset.

dlen is only read when CONFIG_ZLIB is set, so mark it as possibly
unused.

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