Move utils.h and utils.cc from runtime/vm to runtime/platform

runtime/vm/bigint_operations.cc

Index: runtime/vm/bigint_operations.cc
diff --git a/runtime/vm/bigint_operations.cc b/runtime/vm/bigint_operations.cc
index a2696d25b107cc69f7da6b3414fe3c943475b656..70bcd196cc9f5b2dc0a882308ed5f30110ee1fdc 100644
--- a/runtime/vm/bigint_operations.cc
+++ b/runtime/vm/bigint_operations.cc
@@ -1,4 +1,4 @@
-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// 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.
 
@@ -6,10 +6,10 @@
 
 #include <openssl/crypto.h>
 
+#include "platform/utils.h"
 #include "vm/bigint_store.h"
 #include "vm/double_internals.h"
 #include "vm/exceptions.h"
-#include "vm/utils.h"
 #include "vm/zone.h"
 
 namespace dart {