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

runtime/vm/memory_region_test.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/memory_region.h"
 #include "vm/unit_test.h"
 
 namespace dart {
 
 static void* NewRegion(uword size) {
   void* pointer = new uint8_t[size];
   return pointer;
 }
 
@@ skipping 57 matching lines @@
   EXPECT(extended_region.pointer() == region.pointer());
   EXPECT(extended_region.pointer() == sub_region.pointer());
 
   extended_region.Store<int32_t>(0, 42);
   EXPECT_EQ(42, extended_region.Load<int32_t>(0));
 
   DeleteRegion(region);
 }
 
 }  // namespace dart