Comment 3 for bug 795705

;;; Untested, but should work

(in-package :sb-c)

(without-package-locks

(defun undefine-fun-name (name)
  (when name
    (macrolet ((frob (type &optional val)
                 `(unless (eq (info :function ,type name) ,val)
                    (setf (info :function ,type name) ,val))))
      (frob :info)
      (frob :type (specifier-type 'function))
      (frob :where-from :assumed)
      (frob :inlinep)
      (frob :kind)
      (frob :macro-function)
      (frob :inline-expansion-designator)
      (frob :source-transform)
      (frob :structure-accessor)
      (frob :assumed-type)))
  (values))

)