(toplevel): Require `cl' while compiling.
(occur-buffer, occur-nlines): Delete.
(occur-revert-properties): Rename to `occur-revert-properties'.
(occur-mode): Handle it. Set up font lock.
(occur-revert-function): Simply apply `occur-1'.
(occur-mode-find-occurence, occur-mode-mouse-goto)
(occur-mode-goto-occurrence-other-window)
(occur-mode-display-occurrence): Handle buffer property.
(list-matching-lines-face): Use defcustom.
(list-matching-lines-buffer-name-face): New variable.
(occur-accumulate-lines): Renamed from `ibuffer-accumulate-lines',
in ibuffer.el.
(occur-read-primary-args): Move out of `occur'.
(occur): Delete. Now simply call `occur-1'.
(multi-occur, multi-occur-by-filename-regexp): New functions.
(occur-1): New function.
(occur-engine): Renamed from `ibuffer-occur-engine' to replace the
previous implementation of `occur'; taken from ibuf-ext.el.
(occur-fontify-on-property): New function.
(occur-fontify-region-function, occur-unfontify-region-function):
New functions.