Update header.

Update header.
Require 'path-util instead of 'emu.
(quoted-printable-internal-encode-region): Rewrite without regexp.
(quoted-printable-internal-decode-region): Ditto.
(quoted-printable-encode-region): Use read-only `interactive' spec.
(quoted-printable-decode-region): Ditto.
(mime-insert-encoded-file): Use built-in `interactive' spec.
(mime-write-decoded-region): Ditto.
(encoded-text-decode-string): Anchor regexp with "\\`" and "\\'".