[NET]: Fix sparse warnings

Of this type, mostly:

CHECK   net/ipv6/netfilter.c
net/ipv6/netfilter.c:96:12: warning: symbol 'ipv6_netfilter_init' was not declared. Should it be static?
net/ipv6/netfilter.c:101:6: warning: symbol 'ipv6_netfilter_fini' was not declared. Should it be static?

Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/icmp.h b/include/net/icmp.h
index e5ef0d15..6cdebee 100644
--- a/include/net/icmp.h
+++ b/include/net/icmp.h
@@ -57,4 +57,11 @@
 	return (struct raw_sock *)sk;
 }
 
+extern int sysctl_icmp_echo_ignore_all;
+extern int sysctl_icmp_echo_ignore_broadcasts;
+extern int sysctl_icmp_ignore_bogus_error_responses;
+extern int sysctl_icmp_errors_use_inbound_ifaddr;
+extern int sysctl_icmp_ratelimit;
+extern int sysctl_icmp_ratemask;
+
 #endif	/* _ICMP_H */