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

runtime/vm/assert_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/unit_test.h"
 
 
 UNIT_TEST_CASE(Assert) {
   ASSERT(true);
   ASSERT(87 == 87);
   ASSERT(42 != 87);
 }
 
 
@@ skipping 23 matching lines @@
   EXPECT_GT(4, 1);
   EXPECT_GT(2.3, 2.2229);
 
   EXPECT_GE(4, 4);
   EXPECT_GE(15.3, 15.3);
   EXPECT_GE(5, 3);
 
   EXPECT_FLOAT_EQ(15.43, 15.44, 0.01);
   EXPECT_FLOAT_EQ(1.43, 1.43, 0.00);
 }