Added dump of 'redline' objects in 'node dump' XML

Change-Id: I531a04fd4747a4b10858f6317b7c08cceb6458eb
Reviewed-on: https://gerrit.libreoffice.org/6817
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Miklos Vajna <vmiklos@collabora.co.uk>