netstat.1: add various xrefs present in the body to "See Also"

usr.bin/netstat/netstat.1

@@ -1,4 +1,4 @@
-.\"	$NetBSD: netstat.1,v 1.73 2016/05/12 03:44:11 ozaki-r Exp $
+.\"	$NetBSD: netstat.1,v 1.74 2020/07/21 04:58:43 gutteridge Exp $
 .\"
 .\" Copyright (c) 1983, 1990, 1992, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -29,7 +29,7 @@
 .\"
 .\"	@(#)netstat.1	8.8 (Berkeley) 4/18/94
 .\"
-.Dd May 12, 2016
+.Dd July 21, 2020
 .Dt NETSTAT 1
 .Os
 .Sh NAME
@@ -432,12 +432,17 @@ And the fifth character shows the header complete flag status.
 .Xr sockstat 1 ,
 .Xr vmstat 1 ,
 .Xr inet 3 ,
+.Xr kvm 3 ,
+.Xr kvm_openfiles 3 ,
+.Xr sysctl 3 ,
 .Xr bpf 4 ,
+.Xr route 4 ,
 .Xr hosts 5 ,
 .Xr networks 5 ,
 .Xr protocols 5 ,
 .Xr services 5 ,
 .Xr iostat 8 ,
+.Xr route 8 ,
 .Xr trpt 8
 .Sh HISTORY
 The