IPv4/IPv6 Translator Support (RFC 6052)

[dsheets]

There are probably some utility functions we could provide.

See http://tools.ietf.org/html/rfc6052

[dsheets]

http://tools.ietf.org/html/rfc6144 may be related. There is another ipv4 embedding block. We should check the semantic differences between all these v4-in-v6 embeddings.