Fix for TextCtrl problem as reported by Vegh

Move definition of wxMenuItem to /gtk/menuitem.h
  Radical change of how to insert a child into a
    paren window. As C++ doesn't have any VMT in
    a class's consructor, I have to use a callback.
  Fixed culumn resizing bug in wxListCtrl
  Fixed menu height bug in MDI code


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@955 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/defs.h

@@ -21,6 +21,7 @@
 #include "glib.h"
 #include "gdk/gdk.h"
 #include "gtk/gtk.h"
+#include "wx/gtk/win_gtk.h"
 
 #endif