avcodec/snow: check coeffs for validity

Fixes deadlock
Fixes integer overflow
Fixes Ticket 3892

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avfilter/vf_mp: remove incorrect usage of AVFrame.type

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avformat/id3v2: Fix "warning: unused variable uncompressed_buffer_size" if zlib is unavailable

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