Description:
------------
When a class implements an interface which declares a funciton __construct with a given prototype and the class does not follow this prototype, then PHP does not raise a fatal error like in all other cases.

I know that __construct has a lot of special features but I think we need at least a notice for that.

Reproduce code:
---------------
interface constr {
	function __construct();
}

class implem implements constr {
	function __construct ($a) {
	}
}


Expected result:
----------------
Fatal error:  Declaration of implem::__construct() must be compatible with that of constr::__construct() in ...

Actual result:
--------------
5