OS X default fe80::1%lo0 gets removed

[cbednarski]

OS X has a default IPv6 entry for fe80::1%lo0 that gets removed when the hosts file is parsed. The %lo0 segment which indicates that the IP is bound to a specific interface doesn't get parsed correctly.

This could potentially be fixed by adding an exception or using the hosts-specific stuff to clobber, but it won't sort properly unless it's an actual Hostname. Maybe hostname should have an optional field to specify the interface.

Also, I'm not really clear on what the rules are around overlapping names and IPs in this case. Presumably the IPs are unique if bound to different interfaces but since these types of entries are not common (in my experience) I'm not sure how relevant it is to get this 100% correct right now.