   AVAIL-PROPS.
  If a negative prefix arg, then prompt for the properties
   to use, using completion against the candidates in AVAIL-PROPS."
-  (cond ((and arg (natnump (prefix-numeric-value arg)))
+  (cond ((and arg  (natnump (prefix-numeric-value arg)))
          (copy-sequence avail-props))   ; Copy/yank all props available.
         (arg                            ; Prompt for props, from among those available.
          (let ((props-avail  avail-props)

Optional arg FACE is a face symbol.  If non-nil, then delete only
overlays with that FACE."
  (let ((highlight-face  (overlay-get overlay 'hlt-highlight)))
    (when (and highlight-face (or (not face) (eq face highlight-face)))
      (delete-overlay overlay))))

;;; (defun hlt-unhighlight-for-overlay (overlay start end &optional face)

  (let ((oface   (overlay-get overlay 'hlt-highlight))
        (ostart  (overlay-start overlay))
        (oend    (overlay-end   overlay)))
    (when (and oface  (or (not face)  (eq face oface)))
      ;; Either push OVERLAY outside region or split it to exclude region
      ;; or delete it (if it is entirely contained in region).
      (if (< ostart start)
