Super transform - ported from nextgen branch

Super transform - ported from nextgen branch

Various additional changes were made to make the experiment
compatible with misc_fixes.

derflr: +0.979%
hevcmr: +0.865%

Speed-wise with --enable-supertx the encoder is only about 10%
slower than without. Decoding impact is about 30% slowdown.

Note this does not work with ext-tx or var-tx yet. That is
a TODO.

Change-Id: If25af4241a7a9efbd28f58eda3c4f044c7a7ef4b