follows BSD/OS practice and ucd-snmp code (FreeBSD does it for specific
interfaces only).
was: if_lastchange get updated on every packet transmission/receipt.
now: if_lastchange get updated when IFF_UP is changed.
- be persistent on initializing interfaces, even if there's manually-
assigned linklocal, multicast/whatever initialization is necessary.
- do not cache mac addr in the kernel. grab mac addr from existing cards
(this is important when you swap ethernet cards back and forth)
now ppp6 works just fine!
call in6_ifattach() on ATM PVC interface to assign link-local, using
hardware MAC address as seed.
(the change is in sync with kame tree).