Turn off compound inter search refinement for good quality.

Turn this feature off for some modes in  "good" quality.

Change-Id: I3f262d62cca8f01736b977af1465291e8be29f0a
Rd thresholds change with block size.

Added structures to support independent rd thresholds
for different block sizes (and set experimental block
size correction factors).

Added structure to to allow dynamic adaptation of thresholds
per mode and per block size basis depending on how often
the mode/block size combination is seen (currently fixed factor).

Removed some unused variables.

TODO
- Adaptation of thresholds based on how often each mode chosen.
- The baseline mode values could also be adjusted based on
  the block size (e.g. for a particular intra mode use a low threshold
  for 4x4 prediction blocks but a relatively high value for 64x64.

Change-Id: Iddee65ff3324ee309815ae7c1c5a8584720e7568
signs reverted

Change-Id: Ieface458c83eb6e7ee95595d9fc662f372117c9a
Merge "Turn off compound inter search refinement for good quality." into experimental
Merge "Rd thresholds change with block size." into experimental
Bug fix in rd_pick_inter_mode_sb_

Fix the calculation of step size in height.

Change-Id: I0e0c0175f141f5a41214ae51cef233d13942d3c5