more wlans_<ifn> and create_args_<ifn>
Add documentation for these variants and generally update the wireless
device example.
There is are very short lived shim from vaps_<ifn> which produces
a warning and vap_create_<ifn> which does not. Misuse the MFC
notification service to remind me to remove them.
MFC after: 3 weeks
89b5b33da2