This function deletes a previously defined defclass and all its subclasses from the CLIPS environment.
Syntax
(undefclass <class-name>)
If the symbol * is used for <classname>, then all defclasses
will be deleted (unless there exists a defclass called *). The
undefclass command can be used to remove defclasses at any time.
Exceptions: A defclass may not be deleted if it has any instances
or if there is still a reference to it in another loaded construct,
such as a generic function method. This function has no return
value.