Correct the xref section - it was incorrectly using .Fn instead

of .Xr for the xrefs.

lib/libc/gen/getgrent.3

@@ -30,7 +30,7 @@
 .\" SUCH DAMAGE.
 .\"
 .\"     From: @(#)getgrent.3	8.2 (Berkeley) 4/19/94
-.\"	$Id$
+.\"	$Id: getgrent.3,v 1.9 1997/02/22 14:58:07 peter Exp $
 .\"
 .Dd September 29, 1994
 .Dt GETGRENT 3
@@ -167,9 +167,9 @@ have no return value.
 group database file
 .El
 .Sh SEE ALSO
-.Fn getpwent 3 ,
-.Fn yp 4 ,
-.Fn group 5
+.Xr getpwent 3 ,
+.Xr yp 4 ,
+.Xr group 5
 .Sh HISTORY
 The functions
 .Fn endgrent ,