@bind decorator bug when super method is called

This snippet demonstrates that the `bind` decorator does not work correctly on second method call if that method invokes super method which in turn is also decorated:
```javascript
class A {
@bind
f() {
console.log('I\'m A.f');
}
}

class B extends A {
@bind
f() {
console.log('I\'m B.f BEGIN');
super.f();
console.log('I\'m B.f END');
}
}

let b = new B();
console.log('call b.f() 1st time:');
b.f();
console.log('call b.f() 2nd time:');
b.f();
```
Output:
```
call b.f() 1st time:
I'm B.f BEGIN
I'm A.f
I'm B.f END
call b.f() 2nd time:
I'm A.f
```

Start by running the JavaScript reproduction in the issue and compare the first and second calls to b.f(). Then inspect the @bind decorator implementation and its handling of decorated superclass methods. Done means repeated calls preserve the shown B.f and A.f sequence.

Scritto dal modello di indicizzazione a partire dal testo della issue.