[gtkmm-documentation] treemodelcustom: Use the new base class order.

[Murray Cumming <murrayc src gnome org>]

commit 0d214488867060d95a0d35285828e4766bc7a2b6
Author: Murray Cumming <murrayc murrayc com>
Date:   Fri Oct 11 13:31:41 2013 +0200

    treemodelcustom: Use the new base class order.
    
    The previous way is deprecated in the latest glibmm.

 examples/others/treemodelcustom/exampletreemodel.h |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/examples/others/treemodelcustom/exampletreemodel.h 
b/examples/others/treemodelcustom/exampletreemodel.h
index bc0d241..f0d69b2 100644
--- a/examples/others/treemodelcustom/exampletreemodel.h
+++ b/examples/others/treemodelcustom/exampletreemodel.h
@@ -22,8 +22,8 @@
 #include <gtkmm.h>
 
 class ExampleTreeModel
-  : public Glib::Object,
-    public Gtk::TreeModel
+  : public Gtk::TreeModel,
+    public Glib::Object
 {
 protected:
   //Create a TreeModel with @a columns_count number of columns, each of type Glib::ustring.