Rolling new version of Opus.gyp

The new version enables optimizations on iOS.

BUG=
R=henrik.lundin@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/13469004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6060 4adac7df-926f-26a2-2b94-8c16560cd09d