mm-view.el (mm-display-inline-fontify): Make mode optional, and call normal-mode...

mm-view.el (mm-display-inline-fontify): Make mode optional, and call normal-mode if not set. Set temp buffer unmodified to avoid kill-buffer query.
 (mm-inline-text): Render normal text with fontification whenever possible.
gnus-sum.el (gnus-summary-save-parts-1):
gnus-art.el (gnus-article-browse-html-save-cid-content)
 (gnus-article-browse-html-parts, gnus-mime-delete-part)
 (gnus-mime-copy-part, gnus-mime-inline-part, gnus-insert-mime-button):
 Use `mm-handle-filename'.
mm-util.el (mm-handle-filename): New function, return the filename of an handle.