16x16 DCT blocks.

Set on all 16x16 intra/inter modes

Features:
- Butterfly fDCT/iDCT
- Loop filter does not filter internal edges with 16x16
- Optimize coefficient function
- Update coefficient probability function
- RD
- Entropy stats
- 16x16 is a config option

Have not tested with experiments.

hd:     2.60%
std-hd: 2.43%
yt:     1.32%
derf:   0.60%

Change-Id: I96fb090517c30c5da84bad4fae602c3ec0c58b1c