(base64-dl-encode-string): New alias.

(base64-dl-encode-string): New alias.
(base64-dl-decode-string): New alias.
(base64-dl-encode-region): Renamed from `base64-encode-region'; don't
save-excursion and save-restriction.
(base64-dl-decode-region): Renamed from `base64-decode-region'; don't
save-excursion and save-restriction; convert all at once.
(base64-encode-region): New alias.
(base64-decode-region): New alias.