Previously Tx domain rd was used in all cases above speed 0.
Coefficient optimization was only enabled for best and speed 0.

This patch selectively sets these features at other speed settings
based on block complexity.

For the Netflix and HD sets in particular the quality gains are
large compared to the speed hit. At speed 1 the average psnr
gain in the NF set  is > 2.5% with one clip coming in at 18%
and some points almost 30%.  Average gains for the lower
resolution test sets are around 1%.

The gains are biggest at low Q so some further optimization
may be possible.

Change-Id: I340376c7b2a78e5389a34b7ebdc41072808d0576