anchor.diff:  
   (defun clear-all-attribute-cache ()
     (dolist (attribute *attributes*)
  -    (when *attribute-destroy-%internal-value* ; let client clean up
  -      (funcall *attribute-destroy-%internal-value* attribute))
       (setf (get attribute '%attribute-value) nil)))
   
   (defun display-light-p ()
  
positive.code:             (attribute-bold-p attribute)
              (attribute-underline-p attribute))))
  
  ;; 22-Dec-17 stacksmith:
  ;; If internal value needs to be deallocated, set this to (lambda (attribute))
  (defparameter *attribute-destroy-%internal-value* nil)
  
  (defun attribute-p (x)
    (typep x 'attribute))
  
  
negative.code:           syntax-type-attribute
            syntax-builtin-attribute
            completion-attribute
            non-focus-completion-attribute))
  
  (defvar *attributes* '())
  
  