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

runtime/vm/handles_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/flags.h"
 #include "vm/handles.h"
 #include "vm/heap.h"
 #include "vm/object.h"
 #include "vm/unit_test.h"
 #include "vm/zone.h"
 
 namespace dart {
 
 DECLARE_DEBUG_FLAG(bool, trace_handles_count);
@@ skipping 58 matching lines @@
       EXPECT(handle.IsSmi());
       EXPECT_EQ(i, handle.Value());
     }
     EXPECT_EQ((handle_count + (2 * kNumHandles)),
               VMHandles::ScopedHandleCount());
   }
   EXPECT_EQ(handle_count, VMHandles::ScopedHandleCount());
 }
 
 }  // namespace dart