[gtkmm/gtkmm-2-24] Improve the documentation of Gtk::ComboBoxText

[Kjell Ahlstedt <kjellahl src gnome org>]

commit 85a2d7f1e5b8599b9215a4c821b74835298d6bcf
Author: Kjell Ahlstedt <kjell ahlstedt bredband net>
Date:   Wed May 25 18:34:52 2016 +0200

    Improve the documentation of Gtk::ComboBoxText
    
    Bug #766039

 gtk/gtkmm/comboboxtext.h |    8 ++++++++
 1 files changed, 8 insertions(+), 0 deletions(-)
---
diff --git a/gtk/gtkmm/comboboxtext.h b/gtk/gtkmm/comboboxtext.h
index 7f3d413..cae71bd 100644
--- a/gtk/gtkmm/comboboxtext.h
+++ b/gtk/gtkmm/comboboxtext.h
@@ -35,6 +35,14 @@ namespace Gtk
  *
  * You should not call set_model() or attempt to pack more cells into this combo box via its CellLayout base 
class.
  *
+ * You can't use this class with Gtk::Builder::get_widget() or
+ * Gtk::Builder::get_widget_derived() to get a GtkComboBoxText object from a
+ * Glade file. Gtk::ComboBoxText does not wrap GtkComboBoxText, because
+ * Gtk::ComboBoxText was made before GtkComboBoxText, and we don't want to
+ * break the ABI.
+ * This has been fixed in gtkmm 3.x, which is not ABI-compatible with
+ * gtkmm 2.x, and which you are recommended to use.
+ *
  * Note that you cannot use this class with Gnome::Glade::Xml::get_widget_derived() to wrap a GtkComboBox 
added 
  * in the Glade user interface designer, because Glade adds its own TreeModel instead of using the TreeModel 
from 
  * this class. You could use a normal Gtk::ComboBox instead, though you can not use Glade to add rows to a 
TreeModel