ref: a2f33e2505adab7543447d9017f0def0a901a0de
parent: 53729c7786df9e7652e5d52ad88f2b87515a2d52
author: Ronald S. Bultje <rbultje@google.com>
date: Mon Jun 17 10:57:13 EDT 2013
Use assembly-optimized variance functions in sub_pixel_{avg}_var().
2.5% faster when encoding first 50 frames of bus @ 1500kbps.
Change-Id: I5a64703996cf7fd39b07e32c72311c4b125ec6d4