With the sad functions, and hopefully the variance functions soon,
moving to the vpx_dsp location, place the defines used in the
reference C code in a common location.
Change-Id: I4c8ce7778eb38a0a3ee674d2f1c488eda01cfeca
These were established for compatibility. Make sure to use them.
Most frequently they manifest as issues on Visual Studio builds.
Change-Id: I39d764d2eb341b999d7a6132cb44b2acfc511160