Show current line highlighted in *Occur* buffer

Show current line highlighted in *Occur* buffer

* lisp/replace.el (list-matching-lines-current-line-face)
(list-matching-lines-jump-to-current-line): New user options.
(occur--orig-line, occur--orig-line-str): New variables.
(occur, occur-engine): Use them.
(occur--final-pos): New variable.
(occur-1): Use it.
(occur-engine): Idem.
Show the current line with 'list-matching-lines-current-line-face'.
Set point on the first matching line after the current one.
* etc/NEWS: Add entry for the new option.