(authors-aliases): Add, remove, and adjust some entries.

(authors-aliases): Add, remove, and adjust some entries.
(authors-fixed-case, authors-ignored-files, authors-valid-file-names):
(authors-renamed-files-alist): Add entries.
(authors-fixed-entries): Update for renamed and removed files.
(authors-canonical-file-name): Add entries to
authors-checked-files-alist based on their full names, expanded relative
to each log-file directory.
(authors-scan-el, authors-add-to-author-list, authors):
Handle multiple authors in a file, via a new :cowrote category.