Log Message:
Changes 20151227:
* ppc: Add detection of AltiVec support for FreeBSD
* Don't assume 16-byte stack alignment by default on x86-32
* Fix a few static analyzer performance hints
* Revise the row VBV algorithm
* Fix high bit depth lookahead cost compensation algorithm
* Correctly update the intra row predictor in B-frames
* Change the predictors update algorithm