debugger: create actions for 'Stack Up' and 'Stack Down'

There is no shortcut associated with these actions, the user has to
set them up by himself.

src/plugins/debugger/debuggeractions.h

@@ -180,6 +180,8 @@ struct DebuggerManagerActions
     QAction *breakAction;
     QAction *sepAction;
     QAction *reverseDirectionAction;
+    QAction *frameUpAction;
+    QAction *frameDownAction;
 };
 
 } // namespace Internal