bind.2: add references to specific protocol families

Referring the reader to "the manual entries in section 4" was too
unspecific to be useful, as that section contains device drivers as
well.

lib/libc/sys/bind.2

@@ -1,4 +1,4 @@
-.\"	$NetBSD: bind.2,v 1.31 2021/03/28 03:29:31 dholland Exp $
+.\"	$NetBSD: bind.2,v 1.32 2022/06/28 20:24:08 rillig Exp $
 .\"
 .\" Copyright (c) 1983, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -29,7 +29,7 @@
 .\"
 .\"     @(#)bind.2	8.1 (Berkeley) 6/4/93
 .\"
-.Dd March 27, 2021
+.Dd June 28, 2022
 .Dt BIND 2
 .Os
 .Sh NAME
@@ -133,7 +133,9 @@ The name would reside on a read-only file system.
 .Xr connect 2 ,
 .Xr getsockname 2 ,
 .Xr listen 2 ,
-.Xr socket 2
+.Xr socket 2 ,
+.Xr inet 4 ,
+.Xr inet6 4
 .Sh HISTORY
 The
 .Fn bind