Add test case for serializing external references to runtime functions.

test/mjsunit/regress/regress-crbug-465564.js

Index: test/mjsunit/regress/regress-crbug-465564.js
diff --git a/test/mjsunit/deserialize-reference.js b/test/mjsunit/regress/regress-crbug-465564.js
similarity index 65%
copy from test/mjsunit/deserialize-reference.js
copy to test/mjsunit/regress/regress-crbug-465564.js
index b03201315932eab59e38c135d219192e6dcdf0eb..ea0c8dcf66aa4d1b17b1fdc55fffcc25409ca91b 100644
--- a/test/mjsunit/deserialize-reference.js
+++ b/test/mjsunit/regress/regress-crbug-465564.js
@@ -2,7 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --cache=code --serialize-toplevel
+// Flags: --allow-natives-syntax --cache=code
 
-var a = "123";
-assertEquals(a, "123");
+assertEquals(-1, %StringCompare("a", "b"));