Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

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

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Replace ${SYSCTL_W} with ${SYSCTL} in rc.d scripts, as they are identical.
This is a further clean up after r202988.

SYSCTL_W is still initialized in rc.subr as some ports may still use it.

Remove a circular dependency on routing

Submitted by: Mykola Dzham <freebsd@levsha.org.ua>
Approved by: hrs

In regards to the "Starting foo:" type messages at boot time, create and
employ a more generic solution, and use it in the individual rc.d scripts
that also have an $rc_quiet test:

1. Add check_startmsgs() to rc.subr.
2. In the rc.d scripts that use rc_quiet (and rc.subr) substitute
variations of [ -z "$rc_quiet" ] with check_startmsgs
3. In savecore add a trailing '.' to the end of the message to make it
more consistent with other scripts.
4. In newsyslog remove a : before the terminal '.' since we do not expect
there to be anything printed out in between to make it more consistent.
5. In the following scripts change "quotes" to 'quotes' where no variables
exist in the message: savecore pf newsyslog
6. In the following scripts substitute if/then/fi for the simpler (and
more consistent) check_startmsgs &&: faith stf
7. In the following scripts separate the "Starting foo:" from the terminal
'.' to make them more consistent: moused hostname pf
8. In nfsclient move the message to its own line to avoid a style bug
9. In pf rc_quiet does not apply to the _stop method, so remove the
test there.
10. In motd add 'quotes' around the terminal '.' for consistency

Revert the previous afexists() change. Knobs configured explicitly by
the user should not be ignored if possible even if the kernel does not
support the prerequisite feature.

Discussed with: ume

- Add AF_IPX and AF_NATM to afexists().

- Add afexists() check to address family specific rc.d scripts. A
script for an AF will be silently ignored if the kernel has no
support for the AF.

Integrate rc.d/network_ipv6 into rc.d/netif:

- Add rc.d/stf and rc.d/faith for stf(4) and faith(4).
- Remove rc.d/auto_linklocal and rc.d/network_ipv6.
- Move rc.d/sysctl to just before FILESYSTEMS because rc.d/netif
depends on some sysctl variables.

Reviewed by: brooks
MFC after: 3 days