Move assert.h/assert.cc from runtime/vm to runtime/platform

runtime/vm/handles.cc

Index: runtime/vm/handles.cc
diff --git a/runtime/vm/handles.cc b/runtime/vm/handles.cc
index 51bf852950c7c3ca57632264d1ea452cc2209782..fd4e1d32bab33b1e0a2818fcbe70f2a58e7fb367 100644
--- a/runtime/vm/handles.cc
+++ b/runtime/vm/handles.cc
@@ -1,10 +1,10 @@
-// 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.
 
 #include "vm/handles.h"
 
-#include "vm/assert.h"
+#include "platform/assert.h"
 #include "vm/flags.h"
 #include "vm/isolate.h"
 #include "vm/os.h"