[gnome-calculator] Add headerbar and set that as titlebar

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 116e2bfce88c67500aab6024ece232bd53364f9b
Author: Yosef Or Boczko <yoseforb gmail com>
Date:   Mon Nov 25 13:03:17 2013 +0200

    Add headerbar and set that as titlebar
    
    https://bugzilla.gnome.org/show_bug.cgi?id=705909

 src/math-window.vala |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)
---
diff --git a/src/math-window.vala b/src/math-window.vala
index 80242a2..72898b5 100644
--- a/src/math-window.vala
+++ b/src/math-window.vala
@@ -30,6 +30,13 @@ public class MathWindow : Gtk.ApplicationWindow
         role = "gnome-calculator";
         resizable = false;
 
+        var headerbar = new Gtk.HeaderBar ();
+        headerbar.set_title (_("Calculator"));
+        headerbar.show_close_button = true;
+        headerbar.show_fallback_app_menu = true;
+        headerbar.show ();
+        set_titlebar (headerbar);
+
         var main_vbox = new Gtk.Box (Gtk.Orientation.VERTICAL, 0);
         add (main_vbox);
         main_vbox.show ();