On windows, ignore WM_QUERYENDSESSION and close upon WM_ENDSESSION.

The messages can come through CFrame::MSWWindowProc and the wxApp implementation, so make sure to catch both.
Fixes issue 6546.

Source/Core/DolphinWX/Src/Main.h

@@ -33,6 +33,7 @@ private:
 	wxLocale *m_locale;
 
 	void AfterInit(wxTimerEvent& WXUNUSED(event));
+	void OnEndSession(wxCloseEvent& event);
 };
 
 DECLARE_APP(DolphinApp);