latest uribl plugin

Our organization is still discussing sharing some larger portions of our
"forked" qp code.  In the mean time, I haven't sent an update to my uribl
plugin in a while, and we already decided long ago to share that.  Here's
the latest code we're using.  There are only a couple of major changes
that I can think of since we last posted it:

- the uribl plugin now inherits from the 'dnsbl' plugin.  we also have a
prefork/forkserver RBL plugin that inherits from dnsbl; I'm sure we'll be
sharing that soon, too.  we don't have an async RBL plugin yet though, I
don't think.

- fixed an issue that caused high CPU utilization while trying to find
URI's in a message that was obfuscated with a ridiculous method involving
javascript email content using document.write(unencrypt(...))

- ability to query only for A records, while filling in what TXT entries
should stay with static subs.  This saves on DNS traffic; the disadvantage
is that you would obviously not track with any changes to the links or
information given by TXT data from the real servers.

Hope some people find this useful!

-Jared