Modify the portions of RDO using TX-domain coeff calaculations to deal
with TX_COEFF_DEPTH and constant-depth coefficient scaling.  At
present, this represents no functional change.

subset-1:
monty-rest-of-stack-quant-s1@2017-11-13T14:38:43.774Z ->
 monty-rest-of-stack-RDO-s1@2017-11-13T14:39:17.093Z

  PSNR | PSNR Cb | PSNR Cr | PSNR HVS |   SSIM | MS SSIM | CIEDE 2000
0.0000 |  0.0000 |  0.0000 |   0.0000 | 0.0000 |  0.0000 |     0.0000

objective-1-fast --limit=4:
monty-rest-of-stack-quant-o1f4@2017-11-13T14:38:28.828Z ->
 monty-rest-of-stack-RDO-o1f4@2017-11-13T14:38:57.951Z

  PSNR | PSNR Cb | PSNR Cr | PSNR HVS |   SSIM | MS SSIM | CIEDE 2000
0.0000 |  0.0000 |  0.0000 |   0.0000 | 0.0000 |  0.0000 |     0.0000

Change-Id: I0fbc45e018f565f48e1fc8fdeabfcd6cb6fa62fe