reg_sad implementation using SSE2/SSE4.1 intrinsics
Move picture-sse2.c to src/inline-optimizations/.

- Having it in the src dir even though it's not a module on it's own breaks
  the scons build script. It's probably better to have these a little bit
  separated from the normal code anyway.
Move __USE_MINGW_ANSI_STDIO to Makefile.

- I'm not too clear on how this should be used, but having it in the source
  file after mingw stuff was included caused a warning about redefinition of
  __USE_MINGW_ANSI_STDIO.
Merge branch 'sse_intrinsics'