LibJS: Initial class implementation; allow super expressions in object

literal methods; add EnvrionmentRecord fields and methods to
LexicalEnvironment

Adding EnvrionmentRecord's fields and methods lets us throw an exception
when |this| is not initialized, which occurs when the super constructor
in a derived class has not yet been called, or when |this| has already
been initialized (the super constructor was already called).

Libraries/LibJS/Tests/object-basic.js

@@ -70,6 +70,22 @@ try {
     assert(a[2] === 3);
     assert(o4.test === undefined);
 
+    var base = {
+        getNumber() {
+            return 10;
+        }
+    };
+
+    var derived = {
+        getNumber() {
+            return 20 + super.getNumber();
+        }
+    };
+
+    Object.setPrototypeOf(derived, base)
+    assert(derived.getNumber() === 30);
+
+    assertIsSyntaxError("({ foo: function() { super.bar; } })")
     assertIsSyntaxError("({ get ...foo })");
     assertIsSyntaxError("({ get... foo })");
     assertIsSyntaxError("({ get foo })");