Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

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

- Add descriptions to most of the rc scripts. Those are mostly taken from their
daemon's manpage and probably improved.
- Consistently use "filesystem" not "file system".

Approved by: bapt, brueffer
Differential Revision: D452

Set svn:executable to *.

MFC after: 1 month

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.

Localize 'e'.

Submitted by: dougb

Add a new rc.d script, static_arp, which enables the administrator to
statically bind IPv4 <-> MAC address at boot time.

In order to use this, the administrator needs to configure the following
rc.conf(5) variable:

- static_arp_pairs: A list of names for static bind pairs, and,
- a series of static_arp_(name): the arguments that is being passed to
``arp -S'' operation.

Example:
static_arp_pairs="gw"
static_arp_gw="192.168.1.1 00:01:02:03:04:05"

See the rc.conf(5) manual page for more details.

Reviewed by: -rc@
MFC after: 2 weeks