In this experiment, sharp image discontinuity in the predicted
block is detected. Based on this discontinuity, we choose
particular LGTs as row and column transforms.

Bitstream syntax, entropy coding, and RD search for LGT are added.
One binary symbol is used to signal whether LGT is used. This
experiment can work independently with the lgt experiment.

lowres: -0.414% for key frames, -0.151% overall
midres: -0.413% for key frames, -0.161% overall

Change-Id: Iaa2f2c2839c34ca4134fa55e77870dc3f1fa879f