[gtkmm] base.h: Remove unused using Glib::unconst.

[Murray Cumming <murrayc src gnome org>]

commit 654d0a19fff2340e38b31213b60f6834b579d11e
Author: Murray Cumming <murrayc murrayc com>
Date:   Thu Jan 7 08:59:22 2016 +0100

    base.h: Remove unused using Glib::unconst.

 gtk/gtkmm/base.h |    6 ------
 1 files changed, 0 insertions(+), 6 deletions(-)
---
diff --git a/gtk/gtkmm/base.h b/gtk/gtkmm/base.h
index f4c299d..08e1463 100644
--- a/gtk/gtkmm/base.h
+++ b/gtk/gtkmm/base.h
@@ -26,12 +26,6 @@
 #include <glibmm/utility.h>
 #include <glibmm/ustring.h>
 
-namespace Gtk
-{
-  using Glib::unconst;
-
-}
-
 /* This aint pretty, but I don't know a better way to make
    sure things work when the stl classes are defined in a namespace */