A postgresql inet to ip6.arpa snippet

[Erik Kline]

> The icing on the cake would be to support CIDR for this; i.e. if I specify
> 2001:db8::/32 then it becomes 8.b.d.0.1.0.0.2.ip6.arpa

What should it do for a prefix with a CIDR len that doesn't fall on a
nibble boundary?  E.g., what should it produce for 2001:db8::/31, and
/33?