[NETFITLER]: Add nfnetlink layer.

Introduce "nfnetlink" (netfilter netlink) layer.  This layer is used as
transport layer for all userspace communication of the new upcoming
netfilter subsystems, such as ctnetlink, nfnetlink_queue and some day even
the mythical pkttables ;)

Signed-off-by: Harald Welte <laforge@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/Kconfig b/net/Kconfig
index 40a31ba8..02877ac 100644
--- a/net/Kconfig
+++ b/net/Kconfig
@@ -205,6 +205,8 @@
 	  To compile this code as a module, choose M here: the
 	  module will be called pktgen.
 
+source "net/netfilter/Kconfig"
+
 endmenu
 
 endmenu