warning about gui

Note that the GUI especially hasn't been getting a lot of love, and is
probably useful only as a proof-of-concept for now.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>

README

 This package contains commandline and GUI ACL utilities for the Linux
 NFSv4 client.
 
+The GUI is intended as a proof of concept at this point, and hasn't been
+maintained recently.
+
 Copyright UM Regents 2006; see COPYING for license.
 See INSTALL for instructions.