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

The table is MMX-specific and used nowhere else.

Based on a patch by Michael Niedermayer.
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>

Certain instrumentation addons leads to a false positive in configure
and link failures at the end of the build phase.
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>

Original decoder seems to always use 176x128 tiles anyway and this helps
avoiding lots of issues with odd tile sizes in fuzzed files.
Signed-off-by: Anton Khirnov <anton@khirnov.net>