Add check functions for optimized DCT implementations.

Checks are enabled by defining OD_CHECKASM.
doc: fix pdf generation
Use AC_TRY_LINK in tests for intrinics so that a missing intrinsics symbol is noticed.
Add AVX2 intrinsics detection to autotools
Revert Makefile.am changes from previous commit

avx2dct.c is part of a separate patch series, and should have not been included.
Fix AVX2 feature detection
Fix desync by properly clearing mv_grid in the decoder

The desync happens since dd3fca176f087d8fe72ddf2e972d728ef92d941f which
assumes that the grid is cleared. It was reproducable by encoding 16
frames of parkjoy_1080p at -v 50.
upload_commits.sh: Use the full commit message
Remove unused MV visualization code
detailed accounting
Better MV rate estimation
Use mv_small_cdf in estimation