* Remove clone calls from Copy objects
* Used Iterator::cloned() instead of manually cloning
* Pass swf::Function into AvmFunction2::new()
* Use action_clone_sprite
1. We no longer implicitly return Undefined unless we're specifically returning from a function (this also keeps actions from filling the stack with Undefined)
2. With scopes are now always inserted behind the current set of locals rather than overriding them
3. `ActionSubtract` now subtracts (instead of adds)