* include/ruby/win32.h: include windows.h before winsock2.h,
because mswsock.h included by the former uses SOCKET defined
after it in the latter. fix a build failure with VC6.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@51312 b2dd03c8-39d4-4d8f-98ff-823fe69b080e