Several new features and improvements for dartdoc.

lib/compiler/implementation/lib/js_helper.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.
 
-#library('js_helper');
+#library('dart:_js_helper');
 
 #import('coreimpl.dart');
 
 #source('constant_map.dart');
 #source('native_helper.dart');
 #source('regexp_helper.dart');
 #source('string_helper.dart');
 
 // Performance critical helper methods.
 add(var a, var b) => (a is num && b is num)
@@ skipping 1152 matching lines @@
   propertyTypeCastError(value, property);
 }
 
 /**
  * Special interface recognized by the compiler and implemented by DOM
  * objects that support integer indexing. This interface is not
  * visible to anyone, and is only injected into special libraries.
  */
 interface JavaScriptIndexingBehavior {
 }