Fix compiler warnings when using QT_DEPRECATED

Change-Id: If62cff5d1cbd1c8051d709db8747777606797056
Reviewed-by: Samuel Rødal <samuel.rodal@nokia.com>

src/gui/kernel/qguiapplication.h

@@ -85,7 +85,9 @@ public:
     static QWindowList topLevelWindows();
     static QWindow *topLevelAt(const QPoint &pos);
 
+#ifdef QT_DEPRECATED
     static QT_DEPRECATED QWindow *activeWindow() { return focusWindow(); }
+#endif
     static QWindow *focusWindow();
 
     static QScreen *primaryScreen();