use Socket.getifaddrs to show interface names and so on

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46172 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* ext/socket/ifaddr.c (ifaddr_inspect_flags): support IFF_SIMPLEX.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46173 b2dd03c8-39d4-4d8f-98ff-823fe69b080e