Re: [PATCH] Sync of occur-mode with GNU Emacs CVS.

This is a sync of occur-mode with GNU Emacs 22.0.50.1 (CVS). Note that these are 21.5 core lisp files. New features include syntax hightlighting of the matched regular expression, the ability to rename the occur buffer, the ability to search multiple buffers and minor mode that allows movement between the matching lines while remaining in the occur buffer. Since the occur code has started using font-lock features it has been moved out of replace.el into its own files because the necessary functions are not available to replace.el during the dumping stage. This patch also changes the behaviour of read-buffer slightly to conform with GNU Emacs usage: It can return an empty string if 'require-match' is t and 'default' is nil. Previously it would insist that a buffer be entered. A