ip_tunnel: push generic protocol handling to ip_tunnel module.

Process skb tunnel header before sending packet to protocol handler.
this allows code sharing between gre and ovs gre modules.

Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --cc include/net/ip_tunnels.h
Simple merge

diff --cc net/ipv4/gre.c
Simple merge

diff --cc net/ipv4/ip_tunnel.c
Simple merge

diff --cc net/ipv4/ip_tunnel_core.c
Simple merge

diff --cc net/ipv4/ipip.c
Simple merge

diff --cc net/ipv6/sit.c
Simple merge