DHCP server working in production now

[Stephen R. van den Berg]

What follows is a bunch of patches leading up to a working DHCP server
(I use it in several production systems as we speak).

The earlier patches are generic ones, please review and commit if appropriatec.
The last is a patch that replaces parts of the old DHCP core with parts
from my own custom cucidhcp server.  That patch has not been fully reformatted
yet.  Please provide feedback on the implementation.  If it looks right,
I'll clean up that patch too and resubmit it for inclusion.
-- 
Stephen.