use new syntax for connecting to backend signals that enforces explicit connection scope, plus a few other related matters

git-svn-id: svn://localhost/ardour2/branches/3.0@6376 d708f5d6-7413-0410-9779-e7cbd77b26cf

gtk2_ardour/editor_summary.h

@@ -78,6 +78,9 @@ private:
 
 	bool _zoom_dragging;
 	bool _zoom_left;
+
+	PBD::ScopedConnectionList position_connection;
+	PBD::ScopedConnectionList region_property_connection;
 };
 
 #endif