This function deletes a previously defined deffacts.
Syntax
(undeffacts <deffacts-name>)
All facts listed in the deleted deffacts construct will no longer
be asserted as part of a reset. If the symbol * is used for <deffacts-name>,
then all deffacts will be deleted (unless there exists a deffacts
named *). The undeffacts command can be used to remove
deffacts at any time. Exceptions: When deffacts are being reset
as part of the reset command, they cannot be
removed. This function has no return value.