These changes fix a few instances of the following type of warning:
error: ‘void QListWidget::setItemSelected(const QListWidgetItem*, bool)’ is deprecated: Use QListWidgetItem::setSelected() instead [-Werror=deprecated-declarations]
as well as similar warnings for setItemHidden() and
setItemExpanded(). These are just warnings now, but it is planned to
remove the methods for Qt 6:
https://bugreports.qt.io/browse/QTBUG-73048
I tested that LyX can still be built against Qt 4.8.7 with this
commit. Indeed, these methods have been deprecated for a while (it
is just that QT_DEPRECATED_WARNINGS was only turned on by default
starting with 5.13.0). See, e.g.,