This disables a couple of windows warnings that will otherwise
fire on Win64, causing compile failures.

BUG=432375
suppress size_t -> int warnings

R=harryjin@google.com

Review URL: https://webrtc-codereview.appspot.com/24299004

git-svn-id: http://libyuv.googlecode.com/svn/trunk@1171 16f28f9a-4ce2-e073-06de-1de4eb20be90