pf: Make ":0" (noalias) also ignore link-local IPv6 addresses

pf: Make ":0" (noalias) also ignore link-local IPv6 addresses

When users mark an interface to not use aliases they likely also don't
want to use the link-local IPv6 address there.

For example, with the following rule to NAT IPv6:

nat on $ext_if inet6 from $int_if:network to !$int_if:network -> ($ext_if:0)

PF was selecting the link-local address (which comes the first) for the
NAT'ed IPv6 address, which was wrong and broke the NAT setup.

This commit makes PF to ignore the link-local IPv6 addresses so that the
above NAT setup would work.

Obtained-from: FreeBSD (revision 339835, review D17633)
See also: https://lists.freebsd.org/pipermail/freebsd-pf/2014-September/007441.html