Kill some useless headers included in ctnetlink. They aren't used in any 
way.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Index: net-2.6.git/net/ipv4/netfilter/ip_conntrack_netlink.c
===================================================================
--- net-2.6.git.orig/net/ipv4/netfilter/ip_conntrack_netlink.c	2005-11-04 18:02:36.000000000 +0100
+++ net-2.6.git/net/ipv4/netfilter/ip_conntrack_netlink.c	2005-11-04 18:31:02.000000000 +0100
@@ -28,11 +28,8 @@
 #include <linux/netlink.h>
 #include <linux/spinlock.h>
 #include <linux/notifier.h>
-#include <linux/rtnetlink.h>
 
 #include <linux/netfilter.h>
-#include <linux/netfilter_ipv4.h>
-#include <linux/netfilter_ipv4/ip_tables.h>
 #include <linux/netfilter_ipv4/ip_conntrack.h>
 #include <linux/netfilter_ipv4/ip_conntrack_core.h>
 #include <linux/netfilter_ipv4/ip_conntrack_helper.h>