Include all currently present kernel options for IPFW
Also fix igor complaint about manpage/s/man page

Reported by: rgrimes@freebsd.org

PR: 219075
Submitted by: Dries Michiels driesm.michiels_gmail.com
Reported by: rgrimes
Reviewed by: bcr (manpages), 0mp
MFC after: 3 days
Differential Revision: https://reviews.freebsd.org/D24541