QmlDesigner: Fix various compiler warnings

-Wdangling-else
-Wdeprecated-declaration
-Wunused-function
-Wunused-parameter

Change-Id: Id655b6c9c043e2049e921b05619f596b3641bdbd
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>

src/libs/advanceddockingsystem/dockfocuscontroller.cpp

@@ -178,6 +178,8 @@ namespace ADS
 
     void DockFocusController::onApplicationFocusChanged(QWidget *focusedOld, QWidget *focusedNow)
     {
+        Q_UNUSED(focusedOld);
+
         if (d->m_dockManager->isRestoringState())
             return;