[glibmm] Fix some warnings found by clang++.

[Murray Cumming <murrayc src gnome org>]

commit f4b8b84e1acfab3b275578c47f3f21da716737d6
Author: Murray Cumming <murrayc murrayc com>
Date:   Thu Mar 15 12:34:35 2012 +0100

    Fix some warnings found by clang++.
    
    * glib/glibmm/class.cc: registered_derived_type(): Use (void*)0 instead
    of NULL to avoid a missing sentintel warning.

 ChangeLog            |    7 +++++++
 glib/glibmm/class.cc |    2 +-
 2 files changed, 8 insertions(+), 1 deletions(-)
---
diff --git a/ChangeLog b/ChangeLog
index bc1ecc2..115c288 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2012-03-15  Murray Cumming  <murrayc murrayc com>
+
+	Fix some warnings found by clang++.
+
+	* glib/glibmm/class.cc: registered_derived_type(): Use (void*)0 instead
+	of NULL to avoid a missing sentintel warning.
+
 2012-03-16  Josà Alburquerque  <jaalburquerque gmail com>
 
 	Gio::DBus::Object: Add the signals of the interface.
diff --git a/glib/glibmm/class.cc b/glib/glibmm/class.cc
index 8aed786..5f96ec4 100644
--- a/glib/glibmm/class.cc
+++ b/glib/glibmm/class.cc
@@ -74,7 +74,7 @@ void Class::register_derived_type(GType base_type, GTypeModule* module)
     return;
   }
 
-  gchar* derived_name = g_strconcat("gtkmm__", base_query.type_name, NULL);
+  gchar* derived_name = g_strconcat("gtkmm__", base_query.type_name, (void*)0);
   
   if(module)
     gtype_ = g_type_module_register_type(module, base_type, derived_name, &derived_info, GTypeFlags(0));