Subscription: Better cleanup to avoid potential leaks.
Subscription: Better cleanup to avoid potential leaks.

	* src/object/subscription.cc (dtor): Delet cb_ field.
	(stop, unregister): Reset fields no longuer necessary.

urbiforge/urbi,urbiforge/urbi,urbiforge/urbi,aldebaran/urbi,urbiforge/urbi,aldebaran/urbi,urbiforge/urbi,urbiforge/urbi,aldebaran/urbi,urbiforge/urbi,aldebaran/urbi,urbiforge/urbi,aldebaran/urbi,aldebaran/urbi,urbiforge/urbi,aldebaran/urbi,aldebaran/urbi