* elmo-msgdb.el (elmo-msgdb-mark-to-flags): New function.

* elmo-msgdb.el (elmo-msgdb-mark-to-flags): New function.
(elmo-msgdb-flags-to-mark): Ditto.
(elmo-msgdb-append-entity): Ditto.

* elmo-archive.el (elmo-archive-msgdb-create-as-numlist-subr1):
Use `elmo-msgdb-append-entity' instead of construct msgdb.
(elmo-archive-msgdb-create-as-numlist-subr2): Ditto.
(elmo-archive-parse-mmdf): Ditto.

* elmo-cache.el (elmo-folder-msgdb-create): Ditto.

* elmo-filter.el (elmo-folder-msgdb-create): Ditto.

* elmo-localdir.el (elmo-folder-msgdb-create): Ditto.

* elmo-maildir.el (elmo-folder-msgdb-create): Ditto.

* elmo-mark.el (elmo-mark-folder-msgdb-create): Ditto.

* elmo-nmz.el (elmo-folder-msgdb-create): Ditto.

* elmo-sendlog.el (elmo-folder-msgdb-create): Ditto.

* elmo-shimbun.el (elmo-folder-msgdb-create): Ditto.

* elmo-imap4.el (elmo-imap4-fetch-callback-1-subr): Ditto.
(elmo-folder-msgdb-create-plugged): Set elmo-imap4-current-msgdb
to empty msgdb.

* elmo-nntp.el (elmo-nntp-create-msgdb-from-overview-string): Use
`elmo-msgdb-make-message-entity' and `elmo-msgdb-append-entity'
instead of directly construction.
(elmo-nntp-msgdb-create-message): Use `elmo-msgdb-append-entity'
instead of construct msgdb.

* elmo-pop3.el (elmo-pop3-sort-msgdb-by-original-number): Use
`elmo-msgdb-set-overview' instead of reconstruct msgdb.
(elmo-pop3-msgdb-create-message): Use `elmo-msgdb-append-entity'
instead of construct msgdb.