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

runtime/vm/isolate_linux.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/isolate.h"
+
 #include <errno.h>
 #include <pthread.h>
 
-#include "vm/assert.h"
-#include "vm/isolate.h"
+#include "platform/assert.h"
 
 namespace dart {
 
 #define VALIDATE_PTHREAD_RESULT(result)                                        \
   if (result != 0) {                                                           \
     FATAL2("pthread error: %d (%s)", result, strerror(result));                \
   }
 
 
 // The single pthread key which stores all the thread local data for a
@@ skipping 12 matching lines @@
 void Isolate::InitOnce() {
   ASSERT(isolate_key == PTHREAD_KEY_UNSET);
   int result = pthread_key_create(&isolate_key, NULL);
   // Make sure creating a key was successful.
   VALIDATE_PTHREAD_RESULT(result);
   ASSERT(isolate_key != PTHREAD_KEY_UNSET);
   create_callback_ = NULL;
 }
 
 }  // namespace dart