Fix closing editor with ctrl+w or "x" or File > Close

If there are other editors on the document visible in some split, it
should not close the document, but only the editor.

Task-number: QTCREATORBUG-9346
Change-Id: Idce1ae2f518d4c6e875d86f9831d41c46c06361c
Reviewed-by: Eike Ziller <eike.ziller@digia.com>

src/plugins/coreplugin/editortoolbar.h

@@ -93,6 +93,7 @@ signals:
     void splitNewWindowClicked();
     void closeSplitClicked();
     void listSelectionActivated(int row);
+    void listContextMenuRequested(QPoint globalpos);
 
 private slots:
     void updateEditorListSelection(Core::IEditor *newSelection);