(recentf-keep): New option.

(recentf-keep): New option.
(recentf-menu-action): Default to `find-file'.
(recentf-keep-non-readable-files-flag)
(recentf-keep-non-readable-files-p)
(recentf-file-readable-p, recentf-find-file)
(recentf-cleanup-remote): Remove.
(recentf-include-p): More robust.
(recentf-keep-p): New function.
(recentf-remove-if-non-kept): Rename from
`recentf-remove-if-non-readable'. Use `recentf-keep-p'. All
callers updated.
(recentf-menu-items-for-commands): Fix help string.
(recentf-track-closed-file): Update. Doc fix.
(recentf-cleanup): Update. Count removed files. Doc fix.