Xcode: frameworks included with ofxaddon don't get copied to the built product

[ofxSyphon](https://github.com/astellato/ofxSyphon) includes Syphon.framework in libs/Syphon/lib/osx

For addons which have a framework in their lib folder, the framework needs to be added to the Xcode project's Copy Files build phase (which currently copies GLUT.framework) for generated Xcode projects. Doing so fixes the crash on launch caused by the missing framework.
