BUG=348
TESTED=cpplint.py --filter=-casting source/*.cc include/libyuv/*.h
R=harryjin@google.com

Review URL: https://webrtc-codereview.appspot.com/18139004

git-svn-id: http://libyuv.googlecode.com/svn/trunk@1045 16f28f9a-4ce2-e073-06de-1de4eb20be90