[NETNS][FRAGS]: Make the mem counter per-namespace.

This is also simple, but introduces more changes, since
then mem counter is altered in more places.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/ipv6.h b/include/net/ipv6.h
index da1c089..fa80ea4 100644
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -246,7 +246,7 @@
 extern int ipv6_opt_accepted(struct sock *sk, struct sk_buff *skb);
 
 int ip6_frag_nqueues(struct net *net);
-int ip6_frag_mem(void);
+int ip6_frag_mem(struct net *net);
 
 #define IPV6_FRAG_TIMEOUT	(60*HZ)		/* 60 seconds */