Fix for active region's interaction with overlays

fix.el

            ; Fix bug that causes the active region overlay to get the lowest
            ; possible priority.
(eval-after-load 'simple
  '(setq redisplay-highlight-region-function
         (lambda (start end window rol)
           (if (not (overlayp rol))
               (let ((nrol (make-overlay start end)))
                 (funcall redisplay-unhighlight-region-function rol)
                 (overlay-put nrol 'window window)
                 (overlay-put nrol 'face 'region)
                 ;; Normal priority so that a large region doesn't hide all the
                 ;; overlays within it, but high secondary priority so that if it
                 ;; ends/starts in the middle of a small overlay, that small
                 ;; overlay won't hide the region's boundaries.
                 (overlay-put nrol 'priority 100)
                 nrol)
             (unless (and (eq (overlay-buffer rol) (current-buffer))
                          (eq (overlay-start rol) start)
                          (eq (overlay-end rol) end))
               (move-overlay rol start end (current-buffer)))
             ;; mz: Possibly dirty hack to ensure highlight on active region takes its
             ;; rightful place in the overlay priority hierarchy.
             (overlay-put rol 'priority 100)
             rol))))