socket/option.c: use rb_w32_inet_ntop

* ext/socket/option.c (inet_ntop): the fallback implementaion is
  always available on Windows.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48709 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2014-12-05

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48710 b2dd03c8-39d4-4d8f-98ff-823fe69b080e