* wl-vars.el (wl-summary-persistent-mark-priority-list): Add `killed'.

* wl-vars.el (wl-summary-persistent-mark-priority-list): Add `killed'.
(wl-summary-killed-mark): New user option.

* wl-thread.el (wl-thread-update-line-on-buffer-sub): Follow the
API change.
(wl-thread-insert-entity-sub): Ditto.
(wl-thread-recover-messages): New command.

* wl-summary.el (wl-summary-update-mark-and-highlight-window):
Don't call `wl-highlight-summary-current-line' directly.
(wl-summary-buffer-attach): Connect to signal `status-changed'
instead of `cache-changed'.
(wl-summary-buffer-detach): Follow the above change.
(wl-summary-detect-mark-position): Follow the API change.
(wl-summary-rescan-message): Ditto.
(wl-summary-insert-sequential): Ditto.
(wl-summary-update-thread): Ditto.
(wl-summary-message-mark): Ditto.
(wl-summary-persistent-mark): Ditto.
(wl-summary-create-line): Ditto.
(wl-summary-prefetch-region-no-mark): Call
`wl-summary-persistent-mark' with number.
(wl-summary-recover-messages-region): New command.
(wl-summary-target-mark-recover): Ditto.
(wl-summary-recover-message): Ditto.
(wl-summary-persistent-mark-string): Add argument `status' instead
of remove arguments `flags' and `cached'.  Treat killed status.
(wl-summary-update-persistent-mark): Remove optional argument `flags'.

* wl-highlight.el (wl-highlight-summary-displaying-face): New face.
(wl-highlight-summary-line-face-spec): Treat killed status.
(wl-highlight-summary-line-string): Follow the API change.
(wl-highlight-summary-current-line): Ditto.

* elmo.el (cache-changed): Abolish.
(status-changed): New signal.
(elmo-message-killed-p): New generic function and define for
elmo-folder.
(elmo-folder-recover-messages): Ditto.
(elmo-message-set-cached): Emit signal `status-changed' instead of
`cache-changed'.
(elmo-message-status): New macro.
(elmo-message-status-folder): Ditto.
(elmo-message-status-number): Ditto.
(elmo-message-status-set-flags): Ditto.
(elmo-message-status-set-killed): Ditto.
(elmo-message-status-flags): New function.
(elmo-message-status-cached-p): Ditto.
(elmo-message-status-killed-p): Ditto.

* elmo-pipe.el (elmo-pipe-connect-signals): Connect to signal
`status-changed' instead of `cache-changed'.
(elmo-folder-recover-messages): Define.
(elmo-message-killed-p): Ditto.

* elmo-filter.el (elmo-filter-connect-signals): Connect to signal
`status-changed' instead of `cache-changed'.

* elmo-multi.el (elmo-multi-connect-signals): Ditto.
(elmo-message-killed-p): Define.
(elmo-folder-recover-messages): Ditto.