This reverts commit f19700fe52850d051e505ec1b085f25060f7d054.
This crashes in SSE2/SumSquares2DTest.RandomValues/0 under x86 due to
alignment issues
Change-Id: I135d83ba6a7894c09d7c7a139b7eaf876416b40c
Using this we can eliminate large numbers of calls to predict intra,
and is also faster than most of the variance functions it replaces.
This is an equivalence transform so coding performance is unaffected.
Encoder speedup is approx 7% when var_tx, super_tx and ext_tx are all
enabled.
Change-Id: I0d4c83afc4a97a1826f3abd864bd68e41bb504fb