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

when watchdogd is asked to exit nicely (via SIGTERM) it will
stop timer. since watchdogd rc.d script is marked as 'shutdown'
it will exit (on shutdown) and stop timer. if system happens to
hung after watchdogd exited, manual reset is required. when one
operates in "lights-out" type of environments and without
readily available "remote hands" it could create a problem.

this provides ability to override "stop signal" for watchdogd.
default behavior is preserved, i.e. watchdogd will still be killed
via SIGTERM and timer will be stopped. in order to activate new
feature, one needs to put

watchdogd_sig_stop="KILL"

into /etc/rc.conf and also make sure watchdogd timeout is set
to long enough value allowing system to come back online before
timeout fires.

Obtained from: Netflix
MFC after: 1 week

Simply things so that "#REQUIRE: FILESYSTEMS" means the file
systems are fully "ready to go".

'FILESYSTEMS' states: "This is a dummy dependency, for services which
require file systems to be mounted before starting." However, we have
'var' which is was run after 'FILESYSTEMS' and can mount /var if it
already isn't mounted. Furthermore, several scripts cannot use /var
until 'cleanvar' has done its thing. Thus "FILESYSTEMS" hasn't really
meant all critical file systems are fully usable.

start watchdogd before most of other daemons/servers

The main benefit is that watchdogd would shutdown after most of other
daemons/servers and thus, for example, would remedy a system hang caused
by unlucky X server shutdown.

Reviewed by: dougb (earlier version)
MFC after: 2 weeks

Prepare for the removal of set_rcvar() by changing the rcvar=
assignments to the literal values it would have returned.

The concept of set_rcvar() was nice in theory, but the forks
it creates are a drag on the startup process, which is especially
noticeable on slower systems, such as embedded ones.

During the discussion on freebsd-rc@ a preference was expressed for
using ${name}_enable instead of the literal values. However the
code portability concept doesn't really apply since there are so
many other places where the literal name has to be searched for
and replaced. Also, using the literal value is also a tiny bit
faster than dereferencing the variables, and every little bit helps.

Add the shutdown KEYWORD to those scripts that start persistent services
to allow them to do a "clean" shutdown.

I purposely avoided making changes to network-related stuff since the
system shutting down is pretty conclusive, and there may be complicated
dependencies on the network that I would rather not try to unravel.

I also skipped kerberos-related stuff for the reasons above, and
because I have no way to test it.

As previously discussed, add the svn:executable property to all scripts

"REQUIRE: cleanvar" for all RC's writing into /var/run.

Remove the requirement for the FreeBSD keyword as it no longer
makes any sense.

Discussed with: dougb, brooks
MFC after: 3 days

Removes the check for the existence of the sysctl variable
debug.watchdog since it is not created by hardware watchdog(4) devices.
The watchdog(4) device is always compiled in the kernel, so removing the
check should not cause any problems.

Approved by: phk

Mark scripts as not usable inside a jail by adding keyword 'nojail'.

Some suggestions from: rwatson, Ruben de Groot <mail25@bzerk.org>

- Add a software watchdog facility.

This commit has two pieces. One half is the watchdog kernel code which lives
primarily in hardclock() in sys/kern/kern_clock.c. The other half is a userland
daemon which, when run, will keep the watchdog from firing while the userland
is intact and functioning.

Approved by: jeff (mentor)