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

src/gtk/combobox.cpp

@@ -93,6 +93,10 @@ bool wxComboBox::Create(wxWindow *parent, wxWindowID id, const wxString& value,
       GTK_SIGNAL_FUNC(gtk_combo_clicked_callback), (gpointer)this );
   }
   
+  m_parent->AddChild( this );
+
+  (m_parent->m_insertCallback)( m_parent, this );
+  
   PostCreation();
 
   ConnectWidget( GTK_COMBO(m_widget)->button );