Disable IPv6 by default.

[Richi Plana]

Isn't there a way to determine at boot-time whether the network
infrastructure the computer is on actually supports IPv6 or not? For
ubiquitous protocols like IPv4, it isn't needed, but for IPv6, it just
makes more sense. The question is, is it possible to determine it in a
continuous manner? Kind of like hot-plugging. Maybe a check can be
performed everytime an interface goes up (assuming it CAN be detected).
If it isn't used, then free up the unused resources.
--

Richi Plana