avcodec/vc1: fix mb_height for field pictures

Fixes ticket2531

Tables are always allocated now with sufficient space for either progressive
or interlaced content. The alternative would be to detect a change
and reallocate.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/vc1dec: fix mby_start for interlaced content

Fixes first frame of Ticket2531

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/vc1: fix DIFF2/NORM2 with width<=16

Fixes read of uninitialized memory
Fixes msan_uninit-mem_7f785da000e8_585_480i30__codec_WVC1__mode_2__framerate_29.970__type_2__preproc_17.wmv
Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
vp9/x86: idct_add_16x16_ssse3.

Currently only dc-only and full 16x16. Other subforms will follow in the
near future. Total decoding time of ped1080p.webm goes from 9.7 to 9.3
seconds. DC-only goes from 957 -> 131 cycles, and the full IDCT goes
from ~4050 to ~745 cycles.
Merge remote-tracking branch 'rbultje/vp9-simd'

* rbultje/vp9-simd:
  vp9/x86: idct_add_16x16_ssse3.

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