Necessary for a future trellis mode decision/motion estimation patch.
Also add the slowest presets to the regression test.

The output-changing portion of the next patch.

This allows use of the full range of chroma QP offsets, even in combination with the automatic psy-based adjustments.

The cpu_set_t structure is considered opaque.
Also handle sched_getaffinity() error case if "cpusetsize is smaller than the size of the affinity mask used by the kernel."

Replace avcodec_open with avcodec_open2. Now requires libavcodec 53.6.0 or newer.

Problem occurred if pixfmt of lavf/ffms input was PIX_FMT_RGB24 or PIX_FMT_YUV444P.

Much less efficient than YUV444, but easy to support using the YUV444 framework.

Avoid the need to check for corner cases by reordering arithmetic.
Also make a minor optimization to high bit depth predict_16x16_p.

Also remove poc type 1 support (it didn't work anyways) to reduce sps size.

Replace av_open_input_file with avformat_open_input. Now requires libavformat 53.2.0 or newer.

Eliminate the race condition with interframe row predictors and threads.
Recalculate frame_size_estimated at the end of a frame, for improved update_vbv_plan.
Some cosmetics.

Reverts most of r1984 and implements a much simpler solution.

Fix use of deprecated sws_getContext.
Fix uses of sws_format_name.
Fix stream change warning not occurring on the first resolution change.
Drop cpu detection, as it is now performed internally by swscale.
Update swscale version requirements.

Up to ~20-30% faster than SSE2 on Sandy Bridge.

Should allow for some missed compiler optimizations in macroblock_cache_load.