PHP-CPP 2.1.1

• Add automatic builds for g++-4.8 up to g++-8 and clang++-4.0 to clang++-6.0. Also resolves #357 by moving the -shared flag further down on the command line parameters, after the point PHP had the chance to taint them by including the -pie flag.
• If our zend value is a reference, pass through the reference to retrieve the object class entry