Attempt to write a forkable daemon to do dns lookups for
chrooted processes (maild/agentd).


I hope to provide a re-usable support "daemon" that the 
other daemons can use for name lookups. maild would 
fork a copy of os_dns and query it via imsg for the IP
address of the mail server.

os_dns would not be chrooted, but will run with lowered 
privs. unveil and pledge could also be used on OpenBSD
to limit its usefulness to attackers.

Request to os_dns:
* hostname

Reply from os_dns:
* The socket with a connection started


Eventually I'll need to figure out if I want to use this
for udp as well, and how to pass the protocol along.

Todo:

* Cleanup - everything is still too noisy

* errors - I don't think I've handled the errors very well

* kill - there's no way to kill both processes currently

* signals - these need to be gone over

* probably lots of other things

