lavr: mix front center channel as indicated in the ATSC A/52 specification.

When mixing 3 front channels into 2, the center channel is mixed into left and right with the center mix level, not -3dB.
Mirillis FIC video decoder

Does not contain cursor rendering yet.

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
vp9: re-allocate block buffers on uses_2pass change w/o size change.

Fixes valgrind errors and crashes in fuzzed9.ivf.
vp9: some variable re-arrangements for alignment.
Merge commit '76a75c523cd3c63560185394a0a5cd7249db962a'

* commit '76a75c523cd3c63560185394a0a5cd7249db962a':
  lavr: mix front center channel as indicated in the ATSC A/52 specification.

Merged-by: Michael Niedermayer <michaelni@gmx.at>
Merge remote-tracking branch 'qatar/master'

* qatar/master:
  Mirillis FIC video decoder

Conflicts:
	Changelog
	configure
	libavcodec/Makefile
	libavcodec/avcodec.h
	libavcodec/version.h

Merged-by: Michael Niedermayer <michaelni@gmx.at>
vp9: don't allow retaining old segmentation maps after a size change.

Fixes valgrind warnings on fuzzed10.ivf.
g2meet: Rename FRAME_INFO to more appropriate DISPLAY_INFO

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
g2meet: factor out chunk seeking

This version requires fewer code and is safer.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
g2meet: Validate bpp and bitmasks in the display info

That prevents processing of media files with
incompatible or unsupported settings.

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