Fix for missing socket.IPPROTO_IPIP

In bug report https://bitbucket.org/secdev/scapy/issue/5119
it is stated that Solaris has no IPPROTO_IPIP.
The same holds true on windows platform.
Add (monkey patch) missing attribute.
Reference: http://en.wikipedia.org/wiki/List_of_IP_protocol_numbers

--HG--
branch : missing_ipip