The value used for setting the
http://saxon.sf.net/feature/traceListener attribute of
net.sf.saxon.TransformerFactoryImpl currently has to be
an object that implements TraceListener.
However, if setting attributes for Saxon with the
<factory> and <attribute> sub-elements of Ant's xslt
task, the best you can do is set the value to be a String.
The attached patch attempts treats a String value as a
class name and attempts to instantiate and use an
object of the specified class.