FreeBSD if_wg POINTTOPOINT and MULTICAST behaviour

[Jason A. Donenfeld]

Hi Stefan,

WireGuard does not do multicast, so we probably won't set that flag.
You'll want to use babble over unicast anyway.

As far as the `ifconfig wg0 link1` trick I added yesterday goes... I'm
not totally convinced I'll keep that yet for the next snapshot. Does
bird completely ignore interfaces without it? Is there no setting to
change that? Ptp isn't quite a correct match for WireGuard, so having
that flag to satisfy a misbehaving userspace seems like a bummer. Have
you looked everywhere within bird first to see if there's another way?

Jason