Add regression test for issue 1215, expand regression test for issue 1447.

test/mjsunit/regress/regress-1447.js

Index: test/mjsunit/regress/regress-1447.js
===================================================================
--- test/mjsunit/regress/regress-1447.js	(revision 9124)
+++ test/mjsunit/regress/regress-1447.js	(working copy)
@@ -27,3 +27,11 @@
 
 [0].forEach(function(){ Object.freeze(Array.prototype.forEach); });
 [0].every(function(){ Object.seal(Array.prototype.every); });
+
+function testStrict(){
+  "use strict";
+  [0].forEach(function(){ Object.freeze(Array.prototype.forEach); });
+  [0].every(function(){ Object.seal(Array.prototype.every); });
+}
+
+testStrict();