png: add a standalone parser

Useful for reading png images from a pipe.
fate: add utility function to test parser, demuxer, and decoder
fate: add a pngparser test
hevc: Refactor decode_nal_sei_frame_packing_arrangement

Directly set the fields when necessary.

Signed-off-by: Vittorio Giovara <vittorio.giovara@gmail.com>
h264: Refactor decode_frame_packing_arrangement

Directly set the fields when necessary.
apidoc: fix warning from stereo3d.h
vc1: Fix mb_height for field pictures

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

This fixes decoding of a sample.

Signed-off-by: Martin Storsjö <martin@martin.st>
png_parser: Fix parsing on big endian

Since pc.state is populated by shifting in from the end of the
32 bit word, the content within pc.state is already in native endian
and should not be read with the AV_R{L,B} functions.

This was already done correctly for state64 above.

This fixes the fate-corepng test on big endian.

Signed-off-by: Martin Storsjö <martin@martin.st>
Prepare release notes for Libav 10 "Eks"

Additional editing by Diego Biurrun
fate: Explicitly specify the pixel format for the pngparser test

The RGB32 pixel format is RGBA/BGRA depending on target
endianness - make sure to convert it to one specific format for
the framecrc tests.

This fixes the pngparser fate test on big endian.

Signed-off-by: Martin Storsjö <martin@martin.st>