QmlCppEngine: Fix warnings about invalid state changes

Change-Id: Iaa45ff106f5f71a2c7f4729c64c281921b855f80
Reviewed-by: hjk <qthjk@ovi.com>

src/plugins/debugger/qml/qmlcppengine.h

@@ -118,6 +118,7 @@ protected:
     void runEngine();
     void shutdownInferior();
     void shutdownEngine();
+    void quitDebugger();
     void abortDebugger();
 
     void notifyInferiorRunOk();