Stop Transformer from trying to read DTD referenced in XML

[Karr, David]

I have a little standalone test case that I'm developing prior to
building an "xslt" task in Ant.  My main problem right now is that my
sample XML has a DOCTYPE with a systemid specifying a URL to a DTD.
When I try to do the transform, it complains it can't get to the DTD (it
can't get through the firewall).  How do I make it not try to read the
DTD?