In some erroneous fuzzer bistreams, the slice data requires more
parsing than what was implied by the distance between successive
start codes. The primary culprit is the NEXTBITS macro which requires
reading 4 additional bytes of the bitstream buffer. To alleviate
this, 16 bytes per 4x4 TU have been additionally allocated to the
bitstream buffer. Also, chroma bytes are added for 4:2:0/4:2:2.
This is in reference to commit-72315c1, where additional bytes were added to fix similar issue.
Bug = ossfuzz:42538616
Test: mvc_dec_fuzzer