* elmo-imap4.el (elmo-imap4-fetch-callback-1-subr): Follow the API change.

* elmo-imap4.el (elmo-imap4-fetch-callback-1-subr): Follow the API change.
(elmo-folder-msgdb-create-plugged): Ditto.
(elmo-folder-append-messages): Ditto.
(elmo-folder-list-answereds-plugged): Define.
(elmo-imap4-search-internal-primitive): Add `mark' processing.
(elmo-folder-unmark-answered-plugged): Define.
(elmo-folder-mark-as-answered-plugged): Ditto.
(elmo-folder-search-requires-msgdb-p): Ditto.

* elmo-filter.el (elmo-filter-folder): Added new slot 'require-msgdb'.
(elmo-folder-initialize): Set it.
(elmo-folder-msgdb): Define.
(elmo-folder-check): Call elmo-folder-synchronize.
(elmo-folder-close): Define.
(elmo-folder-commit): Ditto.
(elmo-folder-msgdb-create): Rewrite.
(elmo-folder-list-unreads): Ditto.
(elmo-folder-list-importants): Ditto.
(elmo-folder-mark-as-read): Ditto.
(elmo-folder-unmark-read): Ditto.
(elmo-folder-mark-as-important): Ditto.
(elmo-folder-unmark-important): Ditto.
(elmo-folder-mark-as-answered): Define.
(elmo-folder-unmark-answered): Ditto.

* elmo-dop.el (elmo-dop-queue-merge-method-list): Added
elmo-folder-mark-as-answered, elmo-folder-unmark-answered.
(elmo-dop-queue-method-name-alist): Likewise.
(elmo-folder-mark-as-answered-dop): New inline function.
(elmo-folder-unmark-answered-dop): Ditto.
(elmo-folder-status-dop): Treat spool-length as 0 if it does not exist.

* elmo-archive.el (elmo-folder-append-messages): Follow the API change.
(elmo-folder-msgdb-create): Ditto.
(elmo-archive-msgdb-create-as-numlist-subr1): Ditto.
(elmo-archive-msgdb-create-as-numlist-subr2): Ditto.
(elmo-archive-parse-mmdf): Ditto.

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