Move parser and token related libraries into their own subfolder.

pkg/compiler/lib/src/tokens/token_map.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 dart2js.tokens.token_map;
 
 import 'token.dart' show
     Token;
 
 /**
@@ skipping 27 matching lines @@
   Token operator[] (Token key) {
     if (key == null) return null;
     return comments[new TokenKey(key)];
   }
 
   void operator[]= (Token key, Token value) {
     if (key == null) return;
     comments[new TokenKey(key)] = value;
   }
 }