Latest qdoc introduced a new command (\qmlvaluetype) used in
qtdeclarative documentation, as well as other fixes and
improvements.
Pick-to: 6.3
Change-Id: I6453468fb36dbe38d62f5eb9de74beffd568673b
Reviewed-by: Paul Wicking <paul.wicking@qt.io>
Reviewed-by: Kai Koehne <kai.koehne@qt.io>