Add an action to show/hide the mode bar on the far left.

Change-Id: If7a74eed7fc77b1d0fd5e4045671b3767fe2d7a2
Reviewed-by: Petar Perisin <petar.perisin@gmail.com>
Reviewed-by: Eike Ziller <eike.ziller@digia.com>

src/plugins/coreplugin/mainwindow.h

@@ -216,6 +216,7 @@ private:
     QAction *m_exitAction;
     QAction *m_optionsAction;
     QAction *m_toggleSideBarAction;
+    QAction *m_toggleModeSelectorAction;
     QAction *m_toggleFullScreenAction;
     QAction *m_minimizeAction;
     QAction *m_zoomAction;