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

runtime/vm/dart_api_impl_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 "include/dart_api.h"
-
-#include "vm/assert.h"
+#include "platform/assert.h"
 #include "vm/dart_api_impl.h"
 #include "vm/dart_api_state.h"
 #include "vm/thread.h"
 #include "vm/unit_test.h"
 #include "vm/utils.h"
 #include "vm/verifier.h"
 
 namespace dart {
 
 #if defined(TARGET_ARCH_IA32)  // only ia32 can run execution tests.
@@ skipping 2984 matching lines @@
   // We should have received the expected number of interrupts.
   EXPECT_EQ(kInterruptCount, interrupt_count);
 
   // Give the spawned thread enough time to properly exit.
   Isolate::SetInterruptCallback(saved);
 }
 
 #endif  // TARGET_ARCH_IA32.
 
 }  // namespace dart