* ext/socket/mkconstants.rb (TCP_FASTOPEN): Defined for TCP fast open.
  [ruby-core:57048] [Feature #8871] patch by Masaki Matsushita.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42865 b2dd03c8-39d4-4d8f-98ff-823fe69b080e