* lisp/replace.el (list-matching-lines-prefix-face): New defcustom.

* lisp/replace.el (list-matching-lines-prefix-face): New defcustom.
(occur-1): Pass `list-matching-lines-prefix-face' to the function
`occur-engine' if `face-differs-from-default-p' returns t.
(occur-engine): Add `,' inside backquote construct to evaluate
`prefix-face'.  Propertize the prefix with the `prefix-face' face.
Pass `prefix-face' to the functions `occur-context-lines' and
`occur-engine-add-prefix'.
(occur-engine-add-prefix, occur-context-lines): Add optional arg
`prefix-face' and propertize the prefix with `prefix-face'.