Improvements in dired.texi

Improvements in dired.texi

* doc/emacs/dired.texi (Dired): Mention that Dired works with
remote directories.
(Dired Enter): ls-lisp is used on some remote systems as well.
(Dired Navigation): Mention and index the command names.
(Dired Deletion): Document the 'always' value of
dired-recursive-deletes.  Mention the alternative deletion method.
(Marks vs Flags): Fix spelling of Auto-Revert mode.  Document what
marking does on a subdirectory header line.
(Operating on Files): Document that 'Z' uses gzip or compress.
(Comparison in Dired): Mention ediff-files.
(Misc Dired Features): Fix a typo.  Suggested by Michael Albinus
<michael.albinus@gmx.de> in emacs-manual-bugs@gnu.org.