[ruby/resolv] Require win32/resolv just once
And Use Win32::Resolv instead of a constant WINDOWS.
WINDOWS
https://github.com/ruby/resolv/commit/b2c775cd80
[ruby/resolv] Require win32/resolv just once
And Use Win32::Resolv instead of a constant
WINDOWS.https://github.com/ruby/resolv/commit/b2c775cd80