New code from lwip project

lwip repo:
1bf2e31 sockets.c: fixed using unsigned constant 'FIONBIO' in switch on (signed) long
ca26fd1 fixed bug #43778: IPv6 header version not set on 16-bit platform (macro IP6H_VTCFL_SET())
4085a3f task #11472 Support PBUF_REF for RX (IPv6 and IPv4/v6 reassembly might not work yet)

lwip-contrib repo:
bea4a92 Win32 pcapif: - add padding to get the minimum ethernet frame size (strange results when using loopback pcap traffic between 2 simulated hosts); - added: PCAPIF_FILTER_GROUP_ADDRESSES==1: receive all group addressed traffic, not only IP(v4/v6) multicast addresses