* elmo.el (message-number-changed): Define new signal.

* elmo.el (message-number-changed): Define new signal.
* elmo-dop.el (elmo-folder-append-buffer-dop-delayed): Emit
message-number-changed signal.
* elmo-localdir.el (elmo-folder-pack-numbers): Ditto.
* elmo-map.el (elmo-folder-pack-numbers): Ditto.
Respect `elmo-pack-number-check-strict'.

* wl-draft.el (wl-draft-config-info-filename): Extracted from
`wl-draft-config-info-operation'.
(wl-draft-buffer-change-number): New function.
(wl-draft-rename-saved-config): Ditto.
* wl.el (wl-init): Connect slot for message-number-changed.
(toplevel): Add autoload for wl-draft-rename-saved-config.