Make RegExp objects not callable.

test/mjsunit/regress/regress-752.js

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 15 matching lines @@
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 // Test that JSON.stringify correctly unwraps Boolean objects.
 
 // See: http://code.google.com/p/v8/issues/detail?id=752
 
 function replacer(key, value) {
   return value === 42 ? new Boolean(false) : value;
 }
 
-assertEquals(JSON.stringify([42], replacer), "[false]");
+assertEquals("[false]", JSON.stringify([42], replacer));