LightOpenID magic properties do not work with Twig template engine due to lack of __isset

[GoogleCodeExporter]

Adding the following method to the LightOpenID class will make it work with 
Twig (http://twig.sensiolabs.org/):

    function __isset($name) {
        return in_array($name, array('identity', 'trustRoot', 'realm', 'mode'));
    }

Otherwise it throws errors about "Method "mode" for object "LightOpenID" does 
not exist".

Original issue reported on code.google.com by [email protected] on 28 Sep 2013 at 8:51