Update dart:io to convert strings between UTF8 and current code page

tests/standalone/io/process_non_ascii_test.dart

+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:io';
+
+main() {
+  var scriptDir = new File(new Options().script).directorySync();
+  var executable = new File(new Options().executable).fullPathSync();
+  var options = new ProcessOptions();
+  options.workingDirectory = "${scriptDir.path}/æøå";
+  var script = "${scriptDir.path}/æøå.dart";
+  print(options.workingDirectory);
+  Process.run(executable, [script], options).then((result) {
+    Expect.equals(0, result.exitCode);
+  });
+}