Windows: Fix return value of WM_QUERYENDSESSION.

LRESULT should be non-zero if the application can quit,
and it is always handled.

Task-number: QTBUG-35986

Change-Id: Ic8b0ecc731d3efaf94e2a62491918d379fe59f5c
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>

src/plugins/platforms/windows/qwindowscontext.cpp

@@ -969,7 +969,8 @@ bool QWindowsContext::windowsProc(HWND hwnd, UINT message,
         if (lParam & ENDSESSION_LOGOFF)
             fflush(NULL);
 
-        return !sessionManager->wasCanceled();
+        *result = sessionManager->wasCanceled() ? 0 : 1;
+        return true;
     }
     case QtWindows::EndSessionApplicationEvent: {
         QWindowsSessionManager *sessionManager = platformSessionManager();