lingering step 2 of the test rename overhaul: make await tests also a directory

frog/tests/await/single_await_test.dart

 // 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.
 
+// The next line is used to tell test.dart that this test is run by invoking
+// awaitc.dart and passing this file as an argument (e.g. frog
+// frog/await/awaitc.dart test.dart):
+// VMOptions=frog/await/awaitc.dart
+
 // Simple test that transforms the await keyword used at the top-level of a
 // function body.
 
 #import("await_test_helper.dart");
 
 main() {
   final f = futureOf(3);
   final x = await f;
   Expect.equals(3, x);
 }
 
 // This is roughly equivalent to:
 // main() {
 //   final _ret = new Completer();
 //   final f = futureOf(3);
 //   f.then((x) {
 //     Expect.equals(3, x);
 //     _ret.complete(null);
 //   });
 //   Futures.propagateError(f, _ret);
 //   return _ret.future;
 // }