Deferred's valueOf should clean up _props and _super

[Mr0grog]

It seems like not deleting or resetting deferred._super and deferred._props after valueOf() is done could lead to odd behavior, e.g. if someone should happen to hold a reference to the deferred created by def("MyClass") and do something that invokes valueOf() a second (or third, or fourth…) time, unexpected things could happen to the prototype.

While this example is a bit contrived who knows what odd things might occur in real use:

def ("Person") ({
    init: function(name){
        this.name = name;
    },

    speak: function(text){
        alert(text || "Hi, my name is " + this.name);
    }
});

var NinjaDef = def ("Ninja");
NinjaDef << Person ({
    init: function(name){
        this._super();
    },

    kick: function(){
        this.speak("I kick u!");
    }
});

Person ({
    guns: true
});

// This is a bit contrived, but... who knows what odd thing could happen to cause valueOf() to run
NinjaDef + 5;

var ninjy = new Ninja("JDD");
console.log("ninjy.name: ", ninjy.name); // should be JDD
console.log("ninjy.guns: ", ninjy.guns); // Ninjas don't use guns!