Update super to match latest spec.

`super()` now means call the proto of the current function.

Therefore we now need to be explicit with `super.method()`.
This statement would make sense in the commit message (as it happens 'now'), but later we don't know when 'now' is.

I gather that you mean
```
// By spec, extends on an expression causes super() to call Function.prototype
```
?  So somehow `extends null` now makes sense?