1 Let us associate a keyword with either a signed or an unsigned
number. Associate the '-chan' keyword with an unsigned number.
This fixes the defect that crashed 'ifconfig wi0 -chan', reported
by Michael van Elst.
2 Do not try to interpret names as ISO addresses unless the ISO
address family was specified. iso_addr(3) does not report errors,
so it appears to interpret *everything* as an ISO address. This
is a stopgap fix for the defect in 'ifconfig lo0 inet6' on a
!INET6 kernel that deletes the first IPv4 address on lo0.
(Reported by Scott Ellis.)
aa10084492