Creates a constructor that has nothing extra in its scope chain.
function makeCtor (className) {
        function constructor () {
            // Opera has some problems returning from a constructor when Dragonfly isn't running. The || null seems to
            // be sufficient to stop it misbehaving. Known to be required against 10.53, 11.51 and 11.61.
            return this.constructor.apply(this, arguments) || null;
        }
        //<debug>
        if (className) {
            constructor.displayName = className;
        }
        //</debug>
        return constructor;
    }