bug#14722: 24.3.50; dired-x: Have `Z' work for directories as well

[Jambunathan K]

Currently this is what I get for directories.  It should create *.tar.gz
files.

,----
| Loading dired-x...done
| Compress or uncompress org-mode? (y or n)  y
| Compressing /home/kjambunathan/src/org-mode...
| gzip ("-f" "/home/kjambunathan/src/org-mode")
| gzip: /home/kjambunathan/src/org-mode is a directory -- ignored
| Failed to compress/home/kjambunathan/src/org-mode
`----

In GNU Emacs 24.3.50.1 (i686-pc-linux-gnu, GTK+ Version 2.20.1)
 of 2013-06-22 on debian-6.05
Bzr revision: 113135 lekktu@gmail.com-20130622024114-o1weajdmsssio1vk
Windowing system distributor `The X.Org Foundation', version 11.0.10707000
Important settings:
  value of $LANG: en_IN
  locale-coding-system: iso-latin-1-unix
  default enable-multibyte-characters: t