(mime::attribute-char-regexp): New constant.

(mime::attribute-char-regexp): New constant.
(mime::attribute-char-regexp): Ditto.
(mime::attribute-regexp): Ditto.
(mime::ext-octet-regexp): Ditto.
(mime::extended-other-values-regexp): Ditto.
(mime::extended-initial-value-regexp): Ditto.
(mime::parameter-regexp): Match with RFC-2231.
(mime-parse-parameter): Abolished.
(mime-parse-parameters): New function.
(mime-parse-Content-Type): Use `mime-parse-parameters'.
(mime-read-Content-Type): Modify doc-string.
(mime-parse-Content-Disposition): Use `mime-parse-parameters'.