doc: note that cp -l creates _hard_ links

This fact was already noted in the Texinfo manual, but not in the
output of --help.
* src/cp.c (usage): As above, for --help.
Reported by Jari Aalto in http://bugs.debian.org/294327.

THANKS.in

@@ -261,6 +261,7 @@ Jan Moringen                        jan.moringen@uni-bielefeld.de
 Jan Nieuwenhuizen                   janneke@gnu.org
 Jan-Pawel Wrozstinski               jpwroz@gmail.com
 Janos Farkas                        chexum@shadow.banki.hu
+Jari Aalto                          jari.aalto@cante.net
 Jarkko Hietaniemi                   jhi@epsilon.hut.fi
 Jarod Wilson                        jwilson@redhat.com
 Jean Charles Delepine               delepine@u-picardie.fr

src/cp.c

@@ -187,7 +187,7 @@ Mandatory arguments to long options are mandatory for short options too.\n\
   -H                           follow command-line symbolic links in SOURCE\n\
 "), stdout);
       fputs (_("\
-  -l, --link                   link files instead of copying\n\
+  -l, --link                   hard link files instead of copying\n\
   -L, --dereference            always follow symbolic links in SOURCE\n\
 "), stdout);
       fputs (_("\