- Cast function pointers to correct function signatures.
- Increase number of buffers on SATD tests so the initialization doesn't
overflow them and initialize the unused buffers to null.
-Added vzeroupper to satd macro to prevent AVX-SSE transition penalties int picture_x86.asm
-Fixed the order of registers in zero extend macro in picture_x86.asm
-Fixed SATD checkers test pattern in satd_tests.c