x86: SSSE3 LUT-based faster coeff_level_run

~2x faster coeff_level_run.
Faster CAVLC encoding: {1%,2%,7%} overall with {superfast,medium,slower}.
Uses the same pshufb LUT abuse trick as in the previous ads_mvs patch.
lavf input: don't use deprecated AVStream fields

Fixes building against newer libavcodecs from the Libav project.