Reallocate renderbuffer before checking if its dimensions have changed. Fixes #549
Avoid reallocating the renderbuffer if the layer dimensions have not changed
Avoid touching GL at all if a buffer resize isn't required
Merge branch 'fix-ios-renderbuffer' of github.com:notlion/Cinder into notlion-fix-ios-renderbuffer
Merge branch 'notlion-fix-ios-renderbuffer' into glNext
Merge branch 'glNext' of github.com:cinder/Cinder into glNext