Rewrite decodeURL as builtin function, remove now unused runtime functions.

test/mjsunit/regress-612109.js

Index: test/mjsunit/regress-612109.js
diff --git a/test/message/regress/regress-4829-1.js b/test/mjsunit/regress-612109.js
similarity index 54%
copy from test/message/regress/regress-4829-1.js
copy to test/mjsunit/regress-612109.js
index 1ad5feda8cb96cd24e4c47f7407c9699d150c327..a03079a8a7a78344759543566e4242f639e9602d 100644
--- a/test/message/regress/regress-4829-1.js
+++ b/test/mjsunit/regress-612109.js
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-function tag() {}
 
-tag(tag`\xyy`);
+__v_2 = "string for triggering osr in __f_0";
+for (var __v_5 = 0; __v_5 < 16; __v_5++) __v_2 = __v_2 + __v_2;
+decodeURI(encodeURI(__v_2));