Unify most of our utf8 implementations. This takes the implementation

runtime/bin/utf_sources.gypi

Index: runtime/bin/utf_sources.gypi
===================================================================
--- runtime/bin/utf_sources.gypi	(revision 4630)
+++ runtime/bin/utf_sources.gypi	(working copy)
@@ -2,9 +2,18 @@
 # 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.
 
-# This file contains all sources for the dart:io library.
+# This file contains all sources for the dart:utf library.
 {
   'sources': [
-    '../../lib/utf8/utf8.dart',
+    # The utf_vm.dart file needs to be the first source file. It contains
+    # the library and import directives for the dart:utf library. The
+    # dart:utf library is created by concatenating the files listed here
+    # in the order they are listed.
+    '../../lib/utf/utf_vm.dart',
+    
+    '../../lib/utf/utf_core.dart',
+    '../../lib/utf/utf8.dart',
+    '../../lib/utf/utf16.dart',
+    '../../lib/utf/utf32.dart',
   ],
 }