Move Arrays, Collections and Maps into a new library, dart:collections.

tests/corelib/maps_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.
 
 #library("MapsTest.dart");
 #import("dart:coreimpl");
+#import("dart:collection");
 
 main() {
   final key1 = "key1";
   final key2 = "key2";
   final key3 = "key3";
   final key4 = "key4";
   final key5 = "key5";
   final key6 = "key6";
   final key7 = "key7";
   final key8 = "key8";
@@ skipping 108 matching lines @@
   other_map.clear();
 
   // Test Map.putIfAbsent.
   map.clear();
   Expect.equals(false, Maps.containsKey(map, key1));
   Maps.putIfAbsent(map, key1, () => 10);
   Expect.equals(true, map.containsKey(key1));
   Expect.equals(10, map[key1]);
   Expect.equals(10, Maps.putIfAbsent(map, key1, () => 11));
 }