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

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

mdoc: order prologue macros consistently by Dd/Dt/Os

Although groff_mdoc(7) gives another impression, this is the ordering
most widely used and also required by mdocml/mandoc.

Reviewed by: ru
Approved by: philip, ed (mentors)

Use .Nx macro for NetBSD.

Thanks to: Ruslan Ermilov

Credit NetBSD as the source for the /rescue concept.
While I'm here, update my own email address.

Thanks to: Luke Mewburn for pointing out the oversight.

Move the rescue manpage, documenting the new rescue utilities in
/rescue, from section 7 to section 8. The old rescue.7 file has been
simply subjected to "cvs rm", as there is no history to preserve.

Update the release documentation accordingly.

Requested by: njl, ru
Most text by: Tim Kientzle <kientzle@acm.org>
Reviewed by: ru, doc@
Approved by: ceri (mentor)