Make cb4x4 work with daala-ec
Make cb4x4 work with daala-ec

This commit makes the daala-ec work in the cb4x4 mode. As compared
to --enable-experimental, --enable-experimental --enable-cb4x4
improves the coding performance by:

lowres 2.6%
midres 1.2%

Change-Id: Ifee6f011c80364492c4a547513d24eb2958b5a56

GrokImageCompression/aom,smarter/aom,luctrudeau/aom,GrokImageCompression/aom,GrokImageCompression/aom,smarter/aom,luctrudeau/aom,luctrudeau/aom,smarter/aom,GrokImageCompression/aom,smarter/aom,luctrudeau/aom,smarter/aom,GrokImageCompression/aom,smarter/aom,luctrudeau/aom,GrokImageCompression/aom,luctrudeau/aom