Winsock2.

* win32/Makefile.sub (COMMON_HEADERS): include ws2tcpip.h.

* ext/socket/addrinfo.h (addrinfo, getaddrinfo, getnameinfo,
  freehostent, freeaddrinfo): undef before define because these are
  macros in some versions of Windows SDK.

* win32/setup.mak: maybe commit miss.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_1_8_7@16866 b2dd03c8-39d4-4d8f-98ff-823fe69b080e