BUILD: tcp: define SOL_TCP when only IPPROTO_TCP exists

FreeBSD prefers to use IPPROTO_TCP over SOL_TCP, just like it does
with their *_IP counterparts. It's worth noting that there are a few
inconsistencies between SOL_TCP and IPPROTO_TCP in the code, eg on
TCP_QUICKACK. The two values are the same but it's worth applying
what implementations recommend.

No backport is needed, this was uncovered by the recent tcp_info stuff.
1 file changed