* wl-vars.el (wl-folder-process-duplicates-alist): New user option.

* wl-vars.el (wl-folder-process-duplicates-alist): New user option.

* wl-summary.el (wl-summary-buffer-set-folder): Set up `process-duplicates'
 slot.

* wl-highlight.el (wl-highlight-message): Don't highlight as signature
 if detection failed.

* elmo.el (elmo-folder): Added process-duplicates slot.

* elmo-pipe.el (elmo-folder-mark-as-read): Define.
 (elmo-folder-unmark-read): Ditto.
 (elmo-folder-unmark-important): Ditto.
 (elmo-folder-mark-as-important): Ditto.

* elmo-multi.el (elmo-multi-folder-append-msgdb): Implemented
 duplicated message processing.

* elmo.el (elmo-generic-folder-append-msgdb): Ditto.