Minor authors.el updates.

Minor authors.el updates.

* emacs-lisp/authors.el (authors-obsolete-files-regexps):
Ignore VCS-ignore files, and deleted nextstep preferences files.
(authors-ignored-files): Ignore deleted cedet test files, and "*.el".
(authors-ambiguous-files): New list.
(authors-valid-file-names): Add some deleted files.
(authors-renamed-files-alist): Add font-setting.el, edt-user.doc.
(authors-disambiguate-file-name): New function.  (Bug#5501)
(authors-canonical-file-name): Doc fix.
Don't warn about obsolete files.
(authors-canonical-file-name, authors-scan-el):
Use authors-disambiguate-file-name.