This is useful when you want to ensure some little thing happens when you
exit a certain scope.
This patch makes use of it in LibC's netdb code to make sure we close the
connection to the LookupServer.
LookupServer can now take two types of requests:
* L: Lookup
* R: Reverse lookup
The /bin/host program now does a reverse lookup if the input string is a
valid IPv4 address. :^)
We now talk to the lookup server over a local socket and it does the lookup
on our behalf. Including some retry logic, which is nice, because it seems
like DNS requests disappear in the ether pretty damn often where I am.
