Workaround for Ubuntu 12.04 run time warning

"LIBDBUSMENU-GLIB-WARNING **: Trying to remove a child that doesn't believe we're it's parent."
Avoid calling gtk_widget_destroy() on a wxMenuBar attached to a frame
Fixes #14292


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@71648 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/gtk/menu.h

@@ -21,6 +21,7 @@ public:
     wxMenuBar();
     wxMenuBar(long style);
     wxMenuBar(size_t n, wxMenu *menus[], const wxString titles[], long style = 0);
+    ~wxMenuBar();
 
     // implement base class (pure) virtuals
     virtual bool Append( wxMenu *menu, const wxString &title );