Don't require mm-util.

Don't require mm-util.
(quoted-printable-decode-region): Rewritten.
(quoted-printable-decode-string, quoted-printable-encode-region):
Doc fix.
(quoted-printable-encode-region): Barf on multibyte characters.
Maybe make the class multibyte.  Upcase chars, not formatted
strings.  Allow mm-use-ultra-safe-encoding to be unbound.
(quoted-printable-encode-string): Don't use
mm-with-unibyte-buffer.