* elmo.el (elmo-file-tag): New class.

* elmo.el (elmo-file-tag): New class.
(elmo-append-messages-disptch-table): New constant.
(elmo-folder-type-p): New function.
(elmo-folder-append-messages): Redefine as function.

* elmo-null.el (elmo-folder-append-messages): Renamed from
`elmo-folder-append-messages'.

* elmo-maildir.el (elmo-maildir-folder): Inherit `elmo-file-tag'.
(elmo-folder-append-messages-*-maildir): Renamed from
`elmo-folder-append-messages'.

* elmo-localdir.el (elmo-localdir-folder): Inherit
`elmo-file-tag'.
(elmo-folder-append-messages-*-localdir): Renamed from
`elmo-folder-append-messages'.

* elmo-imap4.el (elmo-folder-append-messages-imap4-imap4): Renamed
from `elmo-folder-append-messages'.

* elmo-flag.el (elmo-folder-append-messages-*-flag): Renamed from
`elmo-folder-append-messages'.

* elmo-filter.el (elmo-folder-append-messages-filter-*): New
function.
(elmo-folder-append-messages-*-filter): Ditto.

* elmo-multi.el (elmo-folder-append-messages-multi-*): Ditto.

* elmo-pipe.el (elmo-folder-append-messages-pipe-*): Ditto.
(elmo-folder-append-messages-*-pipe): Renamed from
`elmo-folder-append-messages'.

* elmo-cache.el (elmo-cache-folder): Inherit `elmo-file-tag'.

* elmo-file.el (elmo-file-folder): Ditto.

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

* elmo-archive.el (elmo-folder-append-messages-*-archive): Renamed
from `elmo-folder-append-messages'