Improve IP cloaking

[calzoneman]

Apparently the IPv6 cloak only hashes the first 64 bits, meaning that users with different addresses from the same /64 appear as the same IP (e.g., when banning).

Arguably, CyTube should treat addresses within the same /64 as identical (i.e. instead of requiring a range-IPban, IPban should just ban the /64), but regardless, the cloak hash should also probably expose the fact that the addresses are distinct.