Fixes double-free on error.

The alpha plane is not encoded.

The new name is more consistent with the rest of Libav.

The encoder uses almost none of the mpegvideo infrastructure, only some
fields from MpegEncContext.

The FATE results change because now an all-zero quant matrix is written
into the file. Since it is not used for anything for ljpeg, this should
not be a problem.

This will allow deMpegEncContextizing the LJPEG encoder.

This will allow deMpegEncContextizing the LJPEG encoder.

This will allow deMpegEncContextizing the LJPEG encoder.

Pass the three needed fields from it directly.
This will allow to deMpegEncContextize the LJPEG encoder.

It only needs PutBitContext from it, so pass that directly.

MpegEncContext.aspect_ratio_info is never set for mjpeg, so this was
never written before.

This code was originally added in
5f194811 to h263 to set decoded frame
pts to some random numbers (removed in
a1c5cc42) and then cargo culted to other
decoders.

The code is left in h263dec for now, since some part of the decoder
(apparently OBMC) relies on the specific previous frame to be reused.

This has already been done in eb066a4c,
but the number of frames produced from that file changed due to
timestamps changes since then.

This will allow removing the hacks where each decoder sets
current_picture_ptr on its own.

It is only called from one place in mpegvideo.c now. Also remove the
remove_current parameter, which is always 1.

It is not called from outside of mpegvideo.c anymore.

It is used for encoding only.

It is encoding-only, frame threading is not used for encoding.

The mmxext optimizations should be at least equally fast if available and
amd3dnow optimizations are being deprecated. Thus the former should
override the latter, not the other way around.

Simplifies host/target libc detection splitting.

Fixes an assertion failure in vdpau_get_buffer() when -hwaccel auto is
used, but hwaccel init fails.

Otherwise the expression will be evaluated as unsigned, which will break
when the result should be negative.
CC:libav-stable@libav.org