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: Restore ipfsync

ipfsync is a WIP sync daemon designed to be used in a failover scenario.
It was removed by 5ee61c7daa511927aae8652d6a3ea78866a50ef8. This commit
restores its three files. ipfsync is in my work queue.

MFC after: 10 days
X-MFC with: 5ee61c7daa511927aae8652d6a3ea78866a50ef8