* wl-summary.el (wl-summary-delete-all-msgs): Use

* wl-summary.el (wl-summary-delete-all-msgs): Use
elmo-folder-move-messages instead of elmo-folder-delete-messages
and elmo-folder-detach-messages.

* wl-expire.el (wl-expire-delete): Ditto.
(wl-expire-refile-with-copy-reserve-msg): Ditto.

* elmo.el (elmo-folder-delete-messages): Added notice in docstring.
(elmo-folder-move-messages): Call elmo-global-flag-detach-messages
with argument `delete-if-none' when dst-folder is 'null.

* elmo-flag.el (elmo-folder-append-messages): Defined.
(elmo-global-flag-detach-messages): Added argumnet `delete-if-none'.