Move a bunch of src/ files into subdirectories.

lib/src/util/remote_exception.dart

Index: lib/src/util/remote_exception.dart
diff --git a/lib/src/remote_exception.dart b/lib/src/util/remote_exception.dart
similarity index 98%
rename from lib/src/remote_exception.dart
rename to lib/src/util/remote_exception.dart
index 683b19a18afe3ad05b65677ae216def89c13ccf0..3af88a859133096c439d1bac0eeb648ca8afd445 100644
--- a/lib/src/remote_exception.dart
+++ b/lib/src/util/remote_exception.dart
@@ -2,14 +2,14 @@
 // 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.
 
-library unittest.remote_exception;
+library unittest.util.remote_exception;
 
 import 'dart:async';
 import 'dart:isolate';
 
 import 'package:stack_trace/stack_trace.dart';
 
-import 'expect.dart';
+import '../frontend/expect.dart';
 
 /// An exception that was thrown remotely.
 ///