sbin: Remove ancient SCCS tags.

Remove ancient SCCS tags from the tree, automated scripting, with two
minor fixup to keep things compiling. All the common forms in the tree
were removed with a perl script.

Sponsored by: Netflix

Remove $FreeBSD$: one-line .c comment pattern

Remove /^/[*/]\s*\$FreeBSD\$.*\n/

ipfilter: Removed unused ioctl typedef

Defunct operating systems no longer pollute the ipfilter sources. Remove
their typedefs.

MFC after: 1 week

ipfilter/libipf: printpool_live() consumer ignores return code

The single consumer of printpool_live() ignores the return code.
Avoid wasting resources on this.

MFC after: 2 weeks

ipfilter: Introduce the new FORMAT_IF macro

Interface names stored in the ipstate_t and ipnat_t structures can be
NULL. This occurs when an application, such as named, is running on the
firewall machine itself. For example an application, i.e. named, running
on the firewall itself will cause a state table display and NAT mapping
display to show a null ingress interface and its egress interface. This
is perfectly valid but confusing to human eyes. Rather than print
nothing, print "(null)".

MFC after: 1 week

ipfilter: Move userland bits to sbin

Through fixes and improvements our ipfilter sources have diverged
enough to warrant move from contrib into sbin/ipf. Now that I'm
planning on implementing MSS clamping as in iptables it makes more
sense to move ipfilter to sbin.

This is the second of three commits of the ipfilter move.

Suggested by glebius on two occaions.

Suggested by and discussed with: glebius
Reviewed by: glebius, kp (for #network)
MFC after: 1 month
Differential Revision: https://reviews.freebsd.org/D33510