BUG=116
TEST=xcodebuild/Release/libyuv_unittest --gtest_filter=*I420To*R*Opt
Review URL: https://webrtc-codereview.appspot.com/863015

git-svn-id: http://libyuv.googlecode.com/svn/trunk@402 16f28f9a-4ce2-e073-06de-1de4eb20be90