* gnus-art.el (gnus-mime-copy-part): Find name parameter in Content-Type header

* gnus-art.el (gnus-mime-copy-part): Find name parameter in Content-Type header
 instead of Content-Disposition header.
(gnus-mime-inline-part): Ditto.
(gnus-mime-view-part-as-charset): Ignore charset that the part specifies.

* mm-decode.el (mm-display-part): Work with external parts and usual parts
 similarly.

* mm-extern.el (mm-inline-external-body): Use mm-display-part instead of
 gnus-display-mime.

* mm-util.el (mm-decompress-buffer): Use mm-with-unibyte-buffer instead of
 with-temp-buffer.

* gnus-uu.el (gnus-uu-save-article): Put mml tags instead of part tag to
 summarized topics part in order to encode non-ASCII text.

;; From Kenichi Handa.
* rfc2231.el (rfc2231-decode-encoded-string): Work on unibyte buffer and then
 decode the buffer text if necessary.
(rfc2231-encode-string): Be sure to work on multibyte buffer at first, and
 after mm-encode-body, change the buffer to unibyte.