Building with --enable-dct_only will force the encoder to use only
 tx_type == DCT_DCT.
This experiment gives a loss and is only added for testing.

subset-1:

master@2017-02-21T01:23:58.825Z ->
 master-dct_only@2017-02-21T02:57:28.585Z

  PSNR | PSNR Cb | PSNR Cr | PSNR HVS |   SSIM | MS SSIM | CIEDE 2000
2.5467 |  1.0524 |  0.9171 |   1.8849 | 2.6626 |  2.4995 |     1.8402

objective-1-fast:

master@2017-02-21T01:47:43.790Z ->
 master-dct_only@2017-02-20T16:54:03.578Z

  PSNR | PSNR Cb | PSNR Cr | PSNR HVS |   SSIM | MS SSIM | CIEDE 2000
1.6625 |  0.3948 |  0.3368 |   1.5268 | 1.7142 |  1.7097 |     1.0743

Change-Id: I19b738f3d1a450bc50422149ac42bc184bfae08a