* wl-vars.el (wl-summary-check-line-format): New user option.

* wl-vars.el (wl-summary-check-line-format): New user option.
(wl-summary-line-format-file): Ditto.

* wl-summary.el (wl-summary-buffer-line-format): New buffer local variable.
(wl-summary-buffer-set-folder): Set wl-summary-buffer-line-format.
(wl-summary-goto-folder-subr): Use `wl-summary-line-format-changed-p' and
`wl-summary-view-old-p' to check whether do a rescan or not.
(wl-summary-view-old-p): New function.
(wl-summary-line-format-changed-p): Ditto.
(wl-summary-line-format-save): Ditto.
(wl-summary-save-view-cache): Call `wl-summary-line-format-save'.