(mm-decode-coding-region, mm-encode-coding-region):

(mm-decode-coding-region, mm-encode-coding-region):
Autoload.
(quoted-printable-decode-region):  Rename arg which confused
charset with coding-system.  Don't use nonascii-insert-offset.
Coding-system encode the region initially.  Don't recognize `=='
as valid QP.  Coding-system decode the region finally.
(quoted-printable-decode-string): Rename arg which confused
charset with coding-system.