Implement modular compilation

lib/src/compiler/ast_builder.dart

 // Copyright (c) 2015, 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.
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/src/dart/ast/token.dart';
 import 'package:analyzer/src/generated/utilities_dart.dart';
 import 'package:logging/logging.dart' as logger;
 
@@ skipping 579 matching lines @@
     Label l = new Label(s, new Token(TokenType.COLON, 0));
     return new NamedExpression(l, e);
   }
 
   static VariableDeclarationStatement variableDeclarationStatement(
       VariableDeclarationList varDecl) {
     var semi = new Token(TokenType.SEMICOLON, 0);
     return new VariableDeclarationStatement(varDecl, semi);
   }
 }