x86: ~15% faster predictor checking with subme<3
Branchlessly handle elimination of candidates in MMX roundclip asm.
Fix two bugs in predictor checking
pmv wasn't checked properly in some cases, as well as zero vector.
Output-changing portion of the following patch.
Optimize and organize subme>=3 predictor checking
Also clean up and slightly optimize the subme<3 predictor checking to match.
Add lots of explanatory comments and try to make things a little more understandable.