Add unit tests for post proc.
Add unit tests for post proc.

Some tests are disabled since C and msa don't match sse2.
BUG=webm:1321

Change-Id: I61f303348e5292844a822612f100dbe006489e3e

webmproject/libvpx,Topopiccione/libvpx,mwgoldsmith/vpx,Topopiccione/libvpx,mwgoldsmith/vpx,Topopiccione/libvpx,mwgoldsmith/vpx,Topopiccione/libvpx,ShiftMediaProject/libvpx,Topopiccione/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,mwgoldsmith/libvpx,mwgoldsmith/libvpx,Topopiccione/libvpx,webmproject/libvpx,mwgoldsmith/libvpx,mwgoldsmith/libvpx,mwgoldsmith/vpx,webmproject/libvpx,mwgoldsmith/libvpx,ShiftMediaProject/libvpx,mwgoldsmith/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,webmproject/libvpx,mwgoldsmith/vpx,ShiftMediaProject/libvpx,mwgoldsmith/vpx