Having waited for *way* too long, this is mimir's namecache and trusted domain

Having waited for *way* too long, this is mimir's namecache and trusted domain
cache code.

This uses gencache, mimir's new caching code that stores at text-based cache
of various data.

Mimir has done a *lot* of work on this patch, and it is finally time to
get it in CVS.

Andrew Bartlett
(This used to be commit 47f3bfe9564e7f3aff60cefaefd599e0abb30a31)