(virtual-dired): Declare with `defalias'.

(virtual-dired): Declare with `defalias'.
(dired-mark-unmarked-files, dired-local-variables-file, dired-omit-here-always):
Doc fix.
(dired-omit-mode, dired-find-subdir, dired-enable-local-variables,
dired-clean-up-buffers-too, dired-extra-startup, dired-mark-extension,
dired-jump, dired-jump-other-window, dired-omit-localp, dired-virtual-mode,
dired-smart-shell-command, dired-guess-shell-alist-user, dired-man,
dired-initial-position, dired-x-hands-off-my-keys, dired-x-bind-find-file,
dired-x-submit-report): Fix typos in docstrings.
(dired-mark-unmarked-files): "?\ " -> "?\s".