ext/win32: move

* ext/win32: move from ext/dl and ext/fiddle.  since ext/extmk.rb
  builds extensions in alphabetical order, compiled?('fiddle') under
  ext/dl makes no sense.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41936 b2dd03c8-39d4-4d8f-98ff-823fe69b080e