SilcBool silc_mime_add_multipart(SilcMime mime, SilcMime part);

    Adds a multipart `part` to MIME message `mime'.  The `part' will be
    freed automatically when silc_mime_free is called for `mime'.  Returns
    TRUE if `part' was added to `mime' and FALSE if `mime' is not marked
    as multipart MIME message.

    The silc_mime_set_multipart must be called for `mime' before parts
    can be added to it.  Otherwise FALSE will be returned.

    part = silc_mime_alloc();
    silc_mime_add_field(part, "Content-Type", "image/jpeg");
    silc_mime_add_data(part, data, data_len);

    silc_mime_set_multipart(mime, "mixed", "boundary1");
    silc_mime_add_multipart(mime, part);