Core: Use Qt5-style connects

The heavy lifting was done by clazy.

Change-Id: I2dde14919d917816d02117338205f8f861d8af0a
Reviewed-by: Eike Ziller <eike.ziller@theqtcompany.com>

src/plugins/coreplugin/navigationsubwidget.h

@@ -73,10 +73,8 @@ signals:
     void splitMe(int factoryIndex);
     void closeMe();
 
-private slots:
-    void comboBoxIndexChanged(int);
-
 private:
+    void comboBoxIndexChanged(int);
     void populateSplitMenu();
 
     NavigationWidget *m_parentWidget;