$this isn't used when invoking a ReflectionFunction with Closures

```
Bobs-MacBook-Pro-2:php-src-5.6 bob$ php -r 'class a { private $success = "success\n"; function b() { return new ReflectionFunction(function() { print $this->success; }); } } $a = (new a)->b(); $c = $a->invoke();'

Fatal error: Using $this when not in object context in Command line code on line 1
```

Exactly this issue we are experiencing here — the Closure was passed to ReflectionFunction and `$this` Information will get lost upon `ReflectionFunction::invoke(Args)()`. So, we need to manually rebind the Closure and call it. (well, yeah, `ReflecttionFunction::getClosure()` also isn't bound...)