sccs: Manual changes

For the uncommon items: Go through the tree and remove sccs tags that
didn't fit any nice pattern. If in the neighborhood, other SCM tags were
removed when they were detritis of long-ago CVS somehow in the early
mists of the project. Some adjacent copyrights stringswere removed (they
duplicated the copyright notices in the file). This also removed
non-standard formations of omission of SCCS tags (usually by adding an
extra #if 0 somewhere.

After this commit, a number of strings tagged with the 'what' @(#)
prefix remain, but they are primarily copyright notices.

Sponsored by: Netflix

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/

ipf: Use C89 function definitions.

Reviewed by: zlei
Differential Revision: https://reviews.freebsd.org/D39523

ipfilter userland: Style(9) requires a space after return

Reported by: jrtc27
Fixes: 2582ae5740181e0d2bab10003d66ae91c9b56329
MFC after: 1 month

ipfilter: Adjust userland returns to conform to style(9)

Adjust ipfilter's userland return statements to conform to style(9).

MFC after: 1 month

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