If callout_t is to be used, then <sys/callout.h> should be included.

Fixes the build of ifconfig(8), which failed otherwise.

sys/netinet6/in6_var.h

@@ -1,4 +1,4 @@
-/*	$NetBSD: in6_var.h,v 1.54 2007/10/16 20:31:33 joerg Exp $	*/
+/*	$NetBSD: in6_var.h,v 1.55 2007/10/17 04:35:34 jld Exp $	*/
 /*	$KAME: in6_var.h,v 1.81 2002/06/08 11:16:51 itojun Exp $	*/
 
 /*
@@ -64,6 +64,8 @@
 #ifndef _NETINET6_IN6_VAR_H_
 #define _NETINET6_IN6_VAR_H_
 
+#include <sys/callout.h>
+
 /*
  * Interface address, Internet version.  One of these structures
  * is allocated for each interface with an Internet address.