debugger: slightly saner behaviour for the threads combobox

Change-Id: I20400b037f00a5dbaf11cbbfb184a5bf526883cc
Reviewed-on: http://codereview.qt.nokia.com/4095
Reviewed-by: hjk <qthjk@ovi.com>

src/plugins/debugger/threaddata.h

@@ -60,7 +60,9 @@ struct ThreadData
         LineColumn,
         StateColumn,
         NameColumn,
+        TargetIdColumn,
         CoreColumn,
+        ComboNameColumn,
         ColumnCount = CoreColumn
     };