[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/linux/igmp.h b/include/linux/igmp.h
index 0c31ef0..28f4f3b 100644
--- a/include/linux/igmp.h
+++ b/include/linux/igmp.h
@@ -129,6 +129,9 @@
 #include <linux/skbuff.h>
 #include <linux/in.h>
 
+extern int sysctl_igmp_max_memberships;
+extern int sysctl_igmp_max_msf;
+
 struct ip_sf_socklist
 {
 	unsigned int		sl_max;