Fixed a bug in for-loops when compound is modified

It's a simple fix, but it's basically just shadowing the compound's
name:

  var array = [1];
  for (var i in array) array.pushBack(i); //this will fail

source/toy_vm.c

@@ -482,6 +482,7 @@ static void processEliminate(Toy_VM* vm) {
 }
 
 static void processIterate(Toy_VM* vm) {
+	//URGENT: finish this
 	//ITERATE on [-2] based on type, with [-1] as counter
 	//then delegate to processJump