Move all tests using dart:io to a separate directory

tests/standalone/src/PlatformTest.dart

Index: tests/standalone/src/PlatformTest.dart
diff --git a/tests/standalone/src/PlatformTest.dart b/tests/standalone/src/PlatformTest.dart
deleted file mode 100644
index b6ea96ea0a2632a9415a811a0214f491f03b459d..0000000000000000000000000000000000000000
--- a/tests/standalone/src/PlatformTest.dart
+++ /dev/null
@@ -1,14 +0,0 @@
-// Copyright (c) 2011, 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 p = new Platform();
-  Expect.isTrue(p.numberOfProcessors() > 0);
-  var os = p.operatingSystem();
-  Expect.isTrue(os == "linux" || os == "macos" || os == "windows");
-  var sep = p.pathSeparator();
-  Expect.isTrue(sep == '/' || (os == 'windows' && sep == '\\'));
-}