Another Ruby 1.9 fix for Windows.

* subversion/bindings/swig/ruby/test/windows_util.rb
  (SvnTestUtil.Windows.SetupEnvironment.gen_make_opts): String objects in 1.9
   no longer have the to_a method, so use a workaround that works for both
   1.9 and 1.8.



git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1480738 13f79535-47bb-0310-9956-ffa450edef68