add event stop_propagation

include/nana/gui/notifier.hpp

@@ -1,7 +1,7 @@
 /*
  *	Definition of Notifier
  *	Nana C++ Library(http://www.nanapro.org)
- *	Copyright(C) 2003-2014 Jinhao(cnjinhao@hotmail.com)
+ *	Copyright(C) 2003-2015 Jinhao(cnjinhao@hotmail.com)
  *
  *	Distributed under the Boost Software License, Version 1.0.
  *	(See accompanying file LICENSE_1_0.txt or copy at
@@ -20,6 +20,7 @@ namespace nana
 	class notifier;
 
 	struct arg_notifier
+		: public event_arg
 	{
 		event_code	evt_code;
 		notifier*	notifier_ptr;