GLES2: When running on Linux, use FBO's for RTT's by default.
GLES2: When running on Linux, use FBO's for RTT's by default.

--HG--
extra : rebase_source : 857d7c6c836f1f386e18ca6c7be52915a1674095

vancepym/ogre,nezticle/ogre,jhu-lcsr-forks/ogre,vancepym/ogre,largerussiangames/ogre,jhu-lcsr-forks/ogre,jhu-lcsr-forks/ogre,jhu-lcsr-forks/ogre,nezticle/ogre,vancepym/ogre,largerussiangames/ogre,vancepym/ogre,vancepym/ogre,largerussiangames/ogre,jhu-lcsr-forks/ogre,largerussiangames/ogre,nezticle/ogre,nezticle/ogre