Added sketch for VM

DO NOT MERGE
This is just a sketch.
Please comment.
A function is also an object. In particular this must work:

```js
var f = function() {}
f.x = 1
```

This is important for:
```js
Rect = function() {
  this.w = this.h = 0;
}
Rect.prototype = {
  area: function() { return this.w * this.h }
}

a = new Rect()
a.w = 2
a.h = 3
print(a.area())
```