Deadwood snapshot update

I've updated the documentation to reflect the new behavior for upstream_servers. I have also updated one test: dwood2rc_d_upstream_servers.

Now I have to update all of the tests to use the upstream_servers = {} line. Any test that depends on Deadwood's old round-robin rotating behavior needs to be updated to not depend on that behavior anymore; Deadwood now chooses at random one of the upstream servers before sending a packet upstream.

Since the tests to see that Deadwood is caching data are based on the old behavior, those tests will have to be redone. I will probably do this by getting a packet from upstream, stopping the upstream server, and seeing if Deadwood still answers the hostname in question.

After revising the tests, I need to improve the error messages so when the user has something like upstream_servers["example.com"] = "192.168.72.3" in their dwood2rc file, the program gives a somewhat helpful error message. I also need to make it clear in the documentation that DNS names for upstream_servers must end with a '.' character.

Then I can think about releasing Deadwood 2.4.02.

The snapshot, as always, is at maradns.org/deadwood/snap