SSE2 version of scale is suspected of having a bug, as it didnt work in ARGBInterpolate, while SSSE3 and C do.  Until the result can be verified, SSE2 is disabled.  This will hurt performance on Pentium4 and below.
BUG=49
TEST=none
Review URL: https://webrtc-codereview.appspot.com/672009

git-svn-id: http://libyuv.googlecode.com/svn/trunk@301 16f28f9a-4ce2-e073-06de-1de4eb20be90