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

runtime/vm/isolate_win.cc

-// 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/assert.h"
+#include "platform/assert.h"
 #include "vm/globals.h"
 #include "vm/isolate.h"
 
 namespace dart {
 
 DWORD isolate_key = TLS_OUT_OF_INDEXES;
 
 
 void Isolate::SetCurrent(Isolate* current) {
   ASSERT(isolate_key != TLS_OUT_OF_INDEXES);
   BOOL result = TlsSetValue(isolate_key, current);
   if (!result) {
     FATAL("TlsSetValue failed");
   }
 }
 
 
 void Isolate::InitOnce() {
   ASSERT(isolate_key == TLS_OUT_OF_INDEXES);
   isolate_key = TlsAlloc();
   if (isolate_key == TLS_OUT_OF_INDEXES) {
     FATAL("TlsAlloc failed");
   }
   create_callback_ = NULL;
 }
 
 }  // namespace dart