Speed increase for ext-tx by 20% for a BDRATE drop of 0.26%.
The ext-tx expt becomes -2.66% BDRATE (reduced from -2.92%) for
the lowres set.

It turns out that reducing the set of transforms for intra from
12 to 5 makes very little difference in coding performance (~0.04%).
Most of the performance drop comes from the reduction is transform
set for inter. Currently there is a provision to control that with
a macro.

Change-Id: I7de05527bf72f96acc1e0ab8a74a849da0a141e5