Normalize x64 and ia32 sse2 behavior in libvpx.

BUG=6947196
TEST=trybots

Review URL: https://webrtc-codereview.appspot.com/708009

git-svn-id: http://webrtc.googlecode.com/svn/trunk@2576 4adac7df-926f-26a2-2b94-8c16560cd09d
2 files changed