[NETNS]: Introduce a netns_core structure.

There's already some stuff on the struct net, that should better
be folded into netns_core structure. I'm making the per-proto inuse 
counter be per-net also, which is also a candidate for this, so 
introduce this structure and populate it a bit.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/netns/core.h

@@ -0,0 +1,13 @@
+#ifndef __NETNS_CORE_H__
+#define __NETNS_CORE_H__
+
+struct ctl_table_header;
+
+struct netns_core {
+	/* core sysctls */
+	struct ctl_table_header	*sysctl_hdr;
+
+	int	sysctl_somaxconn;
+};
+
+#endif