NetBSD/usr.sbin/npf/npfctl/todo

-- how to convert other packet filters to npf
-- have a way to use npflog to log packets to syslog
-- have a way to match dropped packets to rules
-- have a way to list the active nat sessions
-- npfctl start does not load if not loaded. It is not clear you need to
   reload first. Or if it loads it should print the error messages.
-- able to specify interfaces before they are created
-- docs/examples out of date
-- npf starts up too late (after traffic can go through)
-- need libpcap in /
-- get better messages from the kernel when things fail

ok npf and dependent modules should autoload automagically as they are used
ok have a way to register cloners? through a mapping file? consistently naming
   the cloner modules? if_cloner? Split if_npflog from the ext_log module and
   added autoloading for cloners.
ok normalise -> normalize (the official project language is US/English)
ok modules should move from /usr/lib to /lib
ok parse dynamic map rule properly inet4($ext_if) does not work
ok create npflog interface automatically
ok need to bring interface npflog up
ok parse 'port "ftp-data"' properly
ok fix usage