- Copy stable/10 (r259064) to releng/10.0 as part of the
10.0-RELEASE cycle.
- Update __FreeBSD_version [1]
- Set branch name to -RC1

[1] 10.0-CURRENT __FreeBSD_version value ended at '55', so
start releng/10.0 at '100' so the branch is started with
a value ending in zero.

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

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

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

Add the 'inet' keyword after the nat rule to avoid interfering with
IPv6.

Update the icmp example to show allowing only the safe types.

Suggested by: Tom Judge <tom at tomjudge.com>
MFC after: 3 days

If the pf.conf(5) example file is copied when setting up a firewall it's
easy to forget about icmp. Update the file to show allowing icmp through
the firewall.

PR: docs/144986
MFC after: 1 month

Update pf examples from OpenBSD to catch up with new stateful defaults and
other syntax changes. Move pf.conf from /etc to examples, too.

Start the dreaded NOFOO -> NO_FOO conversion.

OK'ed by: core

For variables that are only checked with defined(), don't provide
any fake value.

Bring in some examples (and create space for future work here):
- Add OpenBSD example rulesets as advertised in etc/pf.conf and pf.conf(5)
- Tweak the pointer to fit the FreeBSD default location share/examples/pf
- Account for the new directory in BSD.usr.dist (no hier(7) change required
as share/examples is an opaque item there).

Obtained from: OpenBSD
Reminded by: Thomas T. Veldhouse
PR: docs/71691
MFC after: 2 days