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

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

/etc/mail/sendmail.cw is /etc/mail/local-host-names, now.

PR: misc/22262
Submitted by: Michael Bryan <fbsd-security@ursine.com>

Correct $FreeBSD tags to include the (missing) ``:'', restoring the tags
to a useful condition.

Add sample databases for sendmail (access, mailertable, virtusertable),
as well as rename access.txt back to the standard access. Also modify
the Makefile to know how to build hashes for each of these databases.
If one of the databases is missing when Make is run, use a commented
out version of the sample.

Reviewed by: peter
Approved by: jkh