[dns-operations] Reverse Lookup speedup

[Paul Vixie]

> Slaving in-addr.arpa, like FreeBSD does, does not save you a lot of
> lookups. Unlike forward requests, where there are a lot of typos which
> can be catched only by the root, reverse lookups always have an
> existing "TLD" and therefore I suspect that the cache is sufficient.

most of the typo's are before the tld.  slaving every tld on every
recursive server everywhere on the internet seems contraindicated.