4xm: check the return value of read_huffman_tables().

CC:libav-stable@libav.org
av_memcpy_backptr: avoid an infinite loop for back = 0

CC:libav-stable@libav.org
lagarith: avoid infinite loop in lag_rac_refill()

range == 0 happens with corrupted files

CC:libav-stable@libav.org
loco: check that there is data left after decoding a plane.

CC:libav-stable@libav.org
flicvideo: avoid an infinite loop in byte run compression

When byte_run is 0, pixel_countdown is not touched and the loop will run
forever.

CC:libav-stable@libav.org
mov: use the format context for logging.

CC:libav-stable@libav.org
mlpdec: do not try to allocate a zero-sized output buffer.

CC:libav-stable@libav.org
cavs: initialize various context tables to 0

Avoids crashes with corrupted files.

CC:libav-stable@libav.org
qtrle: add more checks against pixel_ptr being negative.

CC:libav-stable@libav.org
qtrle: cosmetics, reformat CHECK_PIXEL_PTR() macro
qtrle: use AV_LOG_ERROR in an error message.