Merge REMI changes.

Merge REMI changes.
* mime-pgp.el (mime-view-application/pgp): Setup local variable
`mime-view-temp-message-buffer' of preview-buffer.
(mime-view-application/pkcs7-mime): Likewise.

* mime-play.el
(mime-preview-quitting-method-for-mime-show-message-mode): Don't
use `mime-entity-buffer'; refer `mime-view-temp-message-buffer'.
(mime-store-message/partial-piece): Use
`insert-file-contents-as-binary' instead of
`(as-binary-input-file (insert-file-contents ...))'; use
`write-region-as-binary' instead of
`(as-binary-output-file (write-region ...)); setup local variable
`mime-view-temp-message-buffer' of preview-buffer.