Fix bugs in parser and update tests to use new directive syntax

compiler/javatests/com/google/dart/compiler/end2end/inc/my.prefixed.app.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.
 
-#import("some.prefixable.lib.dart", prefix: "prefix");
+import "some.prefixable.lib.dart" as prefix;
 
 class Prefix {
   static final int foo = 43;
 
   static getSource() {
     return foo;
   }
 
   static getImport() {
     return prefix.Prefix.foo;
   }
 }