MFC r345450:
Add ability to automatically load ipfw_nat64, ipfw_nptv6 and ipfw_pmod modules by declaring corresponding variables in rc.conf. Also document them in rc.conf(5). Submitted by: Dries Michiels Differential Revision: https://reviews.freebsd.org/D19673
MFC r345985:
Add firewall_[nat64|nptv6|pmod]_enable variables to /etc/defaults/rc.conf