ipv6: add IPV6_HDRINCL option for raw sockets

Same as in Windows, we miss IPV6_HDRINCL for SOL_IPV6 and SOL_RAW.
The SOL_IP/IP_HDRINCL is not available for IPv6 sockets.

Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>