Editor: Add feature for set/unset UTF-8 BOM

Change-Id: Iec7e36b1d7a526d7fa8a8096110b91f9c4cc44f9
Reviewed-by: Leandro Melo <leandro.melo@nokia.com>
Reviewed-by: Eike Ziller <eike.ziller@nokia.com>

src/plugins/texteditor/basetexteditor.h

@@ -260,6 +260,7 @@ public slots:
     virtual void selectAll();
 
     void circularPaste();
+    void switchUtf8bom();
 
     void zoomIn(int range = 1);
     void zoomOut(int range = 1);