Editor: Add action to select word under cursor

Task-number: QTCREATORBUG-641
Change-Id: I83e2705c7250646b13cd3ec52779a1496e6a472c
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/texteditor/texteditor.h

@@ -396,6 +396,7 @@ public:
 
     virtual bool selectBlockUp();
     virtual bool selectBlockDown();
+    void selectWordUnderCursor();
 
     void moveLineUp();
     void moveLineDown();