Get basic superclass method calls working.

test/super/call_other_method.wren

@@ -0,0 +1,22 @@
+class Base {
+  foo {
+    io.write("Base.foo")
+  }
+}
+
+class Derived is Base {
+  bar {
+    io.write("Derived.bar")
+    super.foo
+  }
+}
+
+Derived.new.bar
+// expect: Derived.bar
+// expect: Base.foo
+
+// TODO(bob): Super constructor calls.
+// TODO(bob): Super operator calls.
+// TODO(bob): Calling super outside of a class.
+// TODO(bob): Super calls inside nested functions in methods.
+// TODO(bob): Super where there is no inherited method.