illumos gate

While here, I wonder if it would make sense to split dladm man page into several per-command, or better yet per-object, man pages as done in e.g. git or openzfs' zfs and zpool man pages. That way we could have dladm man page with general data-links description and linking to dladm-iptun, dladm-wifi, dladm-vnic, and so on.

Not while here, but it could make a good followup. Once it's in mdoc it will be easier to deal with.