* lisp/mail/rmail.el: Use lexical-binding

* lisp/mail/rmail.el: Use lexical-binding

(rmail-bury): Remove unused var `buffer-to-bury'.
(rmail-get-new-mail): Remove unused vars `opoint' and `success'.
(rmail-parse-url): Remove unused var `proto', `user', and `host'.
(rmail-unrmail-new-mail-maybe): Remove unused var `new-file'.
(rmail-insert-inbox-text): Remove unused var `movemail'.
(rmail-add-mbox-headers): Remove unused var `limit'.
(rmail-undelete-previous-message): Remove unused var `value'.
(rmail-reply): Remove unused vars `resent-to', `resent-cc',
`resent-reply-to'.
(rmail-mime-mbox-buffer, rmail-mime-view-buffer): Declare.
(rmail-restore-desktop-buffer): Rename arguments.