Add default label to QtMsgType switch statement

This enables us to add a new QtInfoMsg message type to qtbase
without breaking qtxmlpatterns.

Change-Id: Ia4dcee9390eb6b7fc02cf10067317879e931a092
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/xmlpatterns/api/qcoloringmessagehandler.cpp

@@ -130,6 +130,7 @@ void ColoringMessageHandler::handleMessage(QtMsgType type,
         case QtCriticalMsg:
         /* Fallthrough. */
         case QtDebugMsg:
+        default:
         {
             Q_ASSERT_X(false, Q_FUNC_INFO,
                        "message() is not supposed to receive QtCriticalMsg or QtDebugMsg.");