copyright.el updates.

copyright.el updates.

* lisp/emacs-lisp/copyright.el (copyright-at-end-flag)
(copyright-names-regexp): Add safety properties.
(copyright-year-ranges): New option.
(copyright-find-end): New function, split from copyright-update-year.
(copyright-update-year): Use copyright-find-end.
(copyright-fix-years): Optionally, convert years to ranges.
Handle years continued over comment lines.
Do not mess with the fill-prefix.
Do not call copyright-update.
(copyright-update-directory): Optionally, fix years rather than update.
Skip directories.  Find files literally, with only safe local vars.

* etc/NEWS: Mention copyright-fix-years and ranges.