Merging dart:html interfaces and implementations

sdk/lib/html/templates/html/interface/interface_EventTarget.darttemplate

 // 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.
 
 // WARNING: Do not edit - generated code.
 
 part of html;
 
-abstract class EventListenerList {
+abstract class _IEventListenerList {
   EventListenerList add(EventListener handler, [bool useCapture]);
 
   EventListenerList remove(EventListener handler, [bool useCapture]);
 
   bool dispatch(Event evt);
 }
 
-abstract class Events {
+abstract class _IEvents {
   EventListenerList operator [](String type);
 }
 
 $!COMMENT
 abstract class $ID$EXTENDS {
 
   /** @domName EventTarget.addEventListener, EventTarget.removeEventListener, EventTarget.dispatchEvent */
   abstract Events get on;
 $!MEMBERS
 }