Force better lower quantizer keyframe in case of high quantizer.

Change-Id: Ie69a164bc166b6a8819777038d65a7d9f9c3361f
experimental : partition using 1/8 x 1/8 image

The concept:

There's too much noise in source pixels for variance and at low bitrate
the reconstructed looks nothing like the source so we have problems
getting good partitionings with either.   This skirts the issue by using
a box blur scaled down version for variance calculations.  To compare
against source_var_ moved keyframe to be rd based like source_var.

Change-Id: Ie3babdbfadae324b7b5a76bea192893af27f0624
Revert "Change the y4m buffer allocation size"

This reverts commit 72ef1949388c4c0d82769ef06c6db0195b124b13.

Change-Id: Ic1906bcc6da05d2e6529152b92df809c8e5a2406
Merge "Force better lower quantizer keyframe in case of high quantizer."
Merge "experimental : partition using 1/8 x 1/8 image"