#4 XmlRpcException needs to take Throwable

[Will Sargent]

When trying to debug an XML-RPC exception, it can be a
little hard back tracing to where things are from the
original cause to the XmlRpcException.

It would help things considerably if there were an
extra method

public XmlRpcException(String message, Throwable
throwable)

which would show nested exceptions. Note that JDK 1.4
has nested exceptions as a feature of
java.lang.Exception, so this won't be needed by then.