Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Remove the description of the link0 link option, since r215297 the master
media option generally should be used instead. Actually I think the lists
of media types should be removed from the manual pages of MAC drivers
altogether and users just pointed to the output of `ifconfig -m` instead;
even before r215297 there were several outdated descriptions, technically
it's wrong most of the time as not the MAC drivers support these media
types but actually the PHY drivers do and it generally doesn't make sense
to maintain these lists in every manual page of a driver as the media is
auto-detected.

The NetBSD Foundation has granted permission to remove clause 3 and 4 from
their software.

Obtained from: NetBSD

Xref altq(4) for drivers that support it according to altq(4).

Revise markup.

Add missing .El to close list.

This confused the manual page -> hardware notes perl script somewhat and
resulted in part of the output for the stge(4) entry not to be present
in the hardware notes.

Noticed by: brueffer

singular -> plural and a typo fix.

Add a man page for stge(4).