region: Fix a couple of memory leaks

Unref the GSettings object and build the GnomeXkbInfo only
once. There's no need to free and keep rebuilding the latter since it
doesn't keep any state and is a bit expensive to build.

https://bugzilla.gnome.org/show_bug.cgi?id=662489

panels/region/gnome-region-panel-input.c

@@ -870,6 +870,9 @@ setup_input_tabs (GtkBuilder    *builder,
   GtkTreeSelection *selection;
 
   input_sources_settings = g_settings_new (GNOME_DESKTOP_INPUT_SOURCES_DIR);
+  g_object_weak_ref (G_OBJECT (builder), (GWeakNotify) g_object_unref, input_sources_settings);
+
+  if (!xkb_info)
     xkb_info = gnome_xkb_info_new ();
 
 #ifdef HAVE_IBUS