[quadrapassel] Use a header bar on the preferences dialog

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 672fec44cd6b0acf357367f487354e2958207bd7
Author: Michael Catanzaro <mcatanzaro gnome org>
Date:   Sun May 11 18:35:22 2014 -0500

    Use a header bar on the preferences dialog

 src/quadrapassel.vala |    5 ++---
 1 files changed, 2 insertions(+), 3 deletions(-)
---
diff --git a/src/quadrapassel.vala b/src/quadrapassel.vala
index 6965dd6..ee97142 100644
--- a/src/quadrapassel.vala
+++ b/src/quadrapassel.vala
@@ -259,10 +259,9 @@ public class Quadrapassel : Gtk.Application
             return;
         }
 
-        preferences_dialog = new Gtk.Dialog.with_buttons (_("Quadrapassel Preferences"),
+        preferences_dialog = new Gtk.Dialog.with_buttons (_("Preferences"),
                                                           window,
-                                                          (Gtk.DialogFlags)0,
-                                                          _("_Close"), Gtk.ResponseType.CLOSE,
+                                                          Gtk.DialogFlags.USE_HEADER_BAR,
                                                           null);
         preferences_dialog.set_border_width (5);
         var vbox = (Gtk.Box) preferences_dialog.get_content_area ();