don't use shared_from_this for session_impl

include/libtorrent/aux_/session_impl.hpp

@@ -191,7 +191,6 @@ namespace libtorrent
 			, boost::noncopyable
 			, initialize_timer
 			, udp_socket_observer
-			, boost::enable_shared_from_this<session_impl>
 		{
 #if defined TORRENT_VERBOSE_LOGGING || defined TORRENT_LOGGING || defined TORRENT_ERROR_LOGGING
 			// this needs to be destructed last, since other components may log

include/libtorrent/extensions.hpp

@@ -217,7 +217,7 @@ namespace libtorrent
 		{ return boost::shared_ptr<torrent_plugin>(); }
 
 		// called when plugin is added to a session
-		virtual void added(boost::weak_ptr<aux::session_impl>) {}
+		virtual void added(aux::session_impl*) {}
 
 		// called when an alert is posted
 		// alerts that are filtered are not

src/session_impl.cpp

@@ -1549,7 +1549,7 @@ namespace aux {
 
 		m_ses_extensions.push_back(ext);
 		m_alerts.add_extension(ext);
-		ext->added(shared_from_this());
+		ext->added(this);
 	}
 #endif