'does' parameter to attribute construction will now register the type. This
means that it cannot later be redefined as something else. (doy)
+ * $class_type->is_subtype_of no longer returns true if passed the name of the
+ class that the class type represents when the class type wasn't registered.
+ (doy)
+
[OTHER]
* The Class::MOP::load_class and Class::MOP::is_class_loaded subroutines are