* wl-thread.el (wl-thread-update-line-on-buffer-sub): Follow the

* wl-thread.el (wl-thread-update-line-on-buffer-sub): Follow the
argument change in the wl-summary-create-line.
(wl-thread-insert-entity-sub): Ditto.

* wl-summary.el (wl-summary-detect-mark-position): Follow the
argument change in the wl-summary-create-line.
(wl-summary-insert-sequential): Ditto.
(wl-summary-update-thread): Ditto.
(wl-summary-persistent-mark-string): New inline function.
(wl-summary-message-mark): Use it.
(wl-summary-create-line): Abolish argument wl-persistent-mark
and added wl-flags, wl-cached.

* wl-highlight.el (wl-highlight-summary-line-string): Changed argument
mark to flags.
(wl-highlight-summary-current-line): Decide the face not by the
persistent mark but flags.