split of createTrayIconMenu() from createTrayIcon() in BitcoinGUI

- this allows to setup the trayicon before we have and want a trayicon menu
- should be of great use, when we remove that splash screen
- fixes a small bug with the toggleHideAction icon, which is not only used with
  trayicon but also with the Mac dock

src/qt/bitcoingui.h

@@ -105,8 +105,10 @@ private:
     void createMenuBar();
     /** Create the toolbars */
     void createToolBars();
-    /** Create system tray (notification) icon */
+    /** Create system tray icon and notification */
     void createTrayIcon();
+    /** Create system tray menu (or setup the dock menu) */
+    void createTrayIconMenu();
 
 public slots:
     /** Set number of connections shown in the UI */