consider informing about pointer handler children in QQuickItem::itemChange()

    union ItemChangeData {
        ItemChangeData(QQuickItem *v) : item(v) {}
        ItemChangeData(QQuickWindow *v) : window(v) {}
        ItemChangeData(qreal v) : realValue(v) {}
        ItemChangeData(bool v) : boolValue(v) {}

        QQuickItem *item;
        QQuickWindow *window;
        qreal realValue;
        bool boolValue;
    };