in keeping the scripts under rc.d in sync with us. So, begin removal
of NetBSD specific stuff (which made our scripts more complicated
than necessary), starting with the NetBSD KEYWORD.
o group them together so they run one right after another
o use the NetBSD supplied ipfs script instead of tacking
it on to the end of ipnat
o Load the ipl module in ipnat and ipfilter, if it's not already
loaded
o In ipmon and ipnat show a warning if neither ipfilter nor
ipnat is enabled or the ipl module is not loaded, and exit
Approved by: markm (mentor) (implicit)
Tested by: leafy <leafy@leafy.idv.tw>