CONFIG_DAALA_DCT4 currently force-enables CONFIG_DCT_ONLY due to a
missing 4-point DST.  The DST had not been included because it was a
significant coding performance loss; this turned out to be a bug that
has since been corrected.

This patch adds a 4-point type IV DST to the DAALA_DCT4 experiment.
There is a small coding performance loss in using the type IV over
AV1's current type VII.

subset-1:
   monty-newdst4test-baseline-s1-F@2017-07-29T04:58:43.976Z ->
      monty-newdst4test-daala-s1-F@2017-07-29T04:59:56.094Z

   PSNR | PSNR Cb | PSNR Cr | PSNR HVS |    SSIM | MS SSIM | CIEDE 2000
-0.0336 |  0.1393 |  0.0491 |   0.4118 | -0.0439 |  0.2084 |     0.0476

objective-1-fast:
   monty-newdst4test-baseline-o1f-F@2017-07-29T04:58:10.439Z ->
      monty-newdst4test-daala-o1f-F@2017-07-29T04:59:04.678Z

  PSNR | PSNR Cb | PSNR Cr | PSNR HVS |    SSIM | MS SSIM | CIEDE 2000
0.0064 |  0.1071 | -0.0108 |   0.1133 | -0.0035 |  0.0765 |     0.0502

Change-Id: Ie29835edbe0e41bc86f4b09457e88d924cc9bf7e