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>
(cherry picked from commit bde0627e59)

src/plugins/coreplugin/fancytabwidget.h

@@ -159,13 +159,15 @@ public:
     void setTabEnabled(int index, bool enable);
     bool isTabEnabled(int index) const;
 
+    bool isSelectionWidgetVisible() const;
+
 signals:
     void currentAboutToShow(int index);
     void currentChanged(int index);
 
 public slots:
     void setCurrentIndex(int index);
-    void setSelectionWidgetHidden(bool hidden);
+    void setSelectionWidgetVisible(bool visible);
 
 private slots:
     void showWidget(int index);