win32.c: NET_LUID

* configure.in: check for NET_LUID.  header macro varies across
  complier versions.
* win32/win32.c: use configured macro.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41163 b2dd03c8-39d4-4d8f-98ff-823fe69b080e