* wl-util.el (wl-collect-draft): Rewrite with `dolist'.

* wl-util.el (wl-collect-draft): Rewrite with `dolist'.
(wl-inhibit-save-drafts): New internal variable.
(wl-disable-auto-save): Ditto.
(wl-save-drafts): Treat above variables.
(wl-auto-save-drafts): New function.
(wl-set-save-drafts): Split to `wl-start-save-drafts' and
`wl-stop-save-drafts'.
(wl-start-save-drafts): New function.
(wl-stop-save-drafts): Ditto.
(wl-set-auto-save-draft): New command.

* wl-draft.el (wl-draft): Use `wl-start-save-drafts' instead of
`wl-set-save-drafts'.