Have Qt poll for shutdown requested, the QT way.

src/qt/bitcoingui.h

@@ -199,6 +199,9 @@ private slots:
     void showNormalIfMinimized(bool fToggleHidden = false);
     /** Simply calls showNormalIfMinimized(true) for use in SLOT() macro */
     void toggleHidden();
+
+    /** called by a timer to check if fRequestShutdown has been set **/
+    void detectShutdown();
 };
 
 #endif // BITCOINGUI_H