* wl-summary.el (wl-summary-buffer-attach): Connect to signal

* wl-summary.el (wl-summary-buffer-attach): Connect to signal
`update-overview'
(wl-summary-buffer-detach): Disconnect from it.
(wl-summary-rescan-message): Use command.

* wl-message.el (wl-message-buffer-display): Use
`with-current-buffer' instead of `save-excursion'.

* modb.el (elmo-msgdb-update-entity): New API and define generic
implement.

* modb-standard.el (elmo-msgdb-update-entity): Define.

* modb-entity.el (elmo-msgdb-message-entity-update-fields): New
API and define generic implement.

* elmo.el (update-overview): New singnal.

* elmo-shimbun.el (elmo-shimbun-update-overview): Rewrite use
`elmo-msgdb-update-entity' and emit signal `update-overview'.
(elmo-message-entity-parent): Define.

* elmo-pipe.el (elmo-pipe-connect-signals): Connect to signal
`update-overview'.

* elmo-multi.el (elmo-multi-connect-signals): Ditto.

* elmo-filter.el (elmo-filter-connect-signals): Ditto.