x86: Fix SIGILL in high bit-depth intra_sad_x3_4x4_sse2

An SSE3 instruction was used in an SSE2 function.
Fix incorrect row predictor addressing

Somehow managed to not cause things to explode, but was clearly incorrect.
Might improve VBV in some cases to have this working right.
Check malloc during frame dumping
Check pf_log is set in validate_parameters

Help remind people to call x264_param_default in case they didn't read the
documentation.
Merge pull request #1 from Freecom/plain

Plain