add xrefs to readlink(2) and symlink(7). former from Brian Grayson in

PR misc/3378, latter by me.

lib/libc/sys/symlink.2

@@ -1,4 +1,4 @@
-.\"	$NetBSD: symlink.2,v 1.7 1995/02/27 12:38:34 cgd Exp $
+.\"	$NetBSD: symlink.2,v 1.8 1997/03/25 05:18:21 mikel Exp $
 .\"
 .\" Copyright (c) 1983, 1991, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -128,9 +128,11 @@ or
 points outside the process's allocated address space.
 .El
 .Sh SEE ALSO
-.Xr link 2 ,
 .Xr ln 1 ,
-.Xr unlink 2
+.Xr link 2 ,
+.Xr readlink 2 ,
+.Xr unlink 2 ,
+.Xr symlink 7
 .Sh HISTORY
 The
 .Fn symlink