* win32/win32.c (NET_LUID): define it on MinGW32.
  mingw-w64 has NET_LUID but mingw32 (mingw.org) still doesn't have
  NET_LUID. reported by taco on IRC

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41094 b2dd03c8-39d4-4d8f-98ff-823fe69b080e