Ticket #2073 (new enhancement)

Description

This patch makes it possible to have a lazy default parameter of an argument. The attached patch adds an overload on the "defaults" method to Argument. The new method takes a delegate that returns a char[]. If this method has been called the returned value of the delegate takes precedence over the other default parameters when "assigned" is called. This makes it possible, for example, to have a default parameter that is based on the value of another parameter.