[glibmm] Fix the build with --enable-warnings=fatal

[Kjell Ahlstedt <kjellahl src gnome org>]

commit 0b6912c7b13ea7eb840e0349c1efc531b7502414
Author: Kjell Ahlstedt <kjell ahlstedt bredband net>
Date:   Wed Sep 23 08:59:38 2015 +0200

    Fix the build with --enable-warnings=fatal
    
    * glib/glibmm/objectbase.cc: Cast pointers to void* in call to g_warning().

 glib/glibmm/objectbase.cc |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/glib/glibmm/objectbase.cc b/glib/glibmm/objectbase.cc
index 1a1f522..080949d 100644
--- a/glib/glibmm/objectbase.cc
+++ b/glib/glibmm/objectbase.cc
@@ -229,7 +229,8 @@ void ObjectBase::_move_current_wrapper(GObject* object, Glib::ObjectBase* previo
     g_warning("%s: Unexpected previous wrapper, for object of type %s.\n"
               "previous_wrapper=%p, current_wrapper=%p",
                 G_STRFUNC, G_OBJECT_TYPE_NAME(object),
-                previous_wrapper, current_wrapper);
+                static_cast<void*>(previous_wrapper),
+                static_cast<void*>(current_wrapper));
   }
 
   //Remove the previous wrapper, without invoking destroy_notify_callback_():