Adding support to append Separator Items for MenuButton

Updated PanelBar to use this API

src/gui/widgets/menu-button.cpp

@@ -101,6 +101,16 @@ MenuButton::append (const char *slug, const char* title,
   append (uSlug, uTitle, callback);
 }
 
+void
+MenuButton::appendSeparator()
+{
+  uimanager->add_ui_separator(
+      uimanager->new_merge_id(),
+      ustring("ui/").append(POPUP_SLUG),
+      "Separator", Gtk::UI_MANAGER_SEPARATOR,
+      false);
+}
+
 void
 MenuButton::popup()
 {

src/gui/widgets/menu-button.hpp

@@ -79,9 +79,27 @@ public:
    */
   Menu& get_menu();
   
+  /**
+   * Append a Menu Item to the Menu
+   * @param slug Unique identifier in the UI Manager
+   * @param title The title of the item
+   * @param callback The signal handler when clicked
+   */
   void append (uString &slug, uString &title, sigc::slot<void>& callback);
+
+  /**
+   * Append a Menu Item to the Menu
+   * @param slug Unique identifier in the UI Manager
+   * @param title The title of the item
+   * @param callback The signal handler when clicked
+   */
   void append (const char *slug, const char* title, sigc::slot<void>& callback);
 
+  /**
+   * Append a Gtk::SeparatorMenuItem to the Menu
+   */
+  void appendSeparator();
+
   /**
    * Pops up the menu.
    */

src/gui/widgets/panel-bar.cpp

@@ -83,10 +83,7 @@ PanelBar::setup_panel_button()
       **/
     }
 
-  FIXME("Update for gtk3");
-#if 0
-  list.push_back( Menu_Helpers::SeparatorElem() );
-#endif
+  panelButton.appendSeparator();
 
   // Add extra commands
   slot<void> hide = mem_fun(*this, &PanelBar::on_hide);