Avoid calling the builtin String.prototype.split in Intl

test/intl/regress-5179.js

+// Copyright 2016 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+Object.defineProperty(String.prototype, Symbol.split, {
+    get() {
+        return function(obj, limit) {
+            return [, null];
+        }
+    }
+});
+
+dtf = new Intl.DateTimeFormat("de", {timeZone:"America/bueNos_airES"});
+
+assertEquals("America/Buenos_Aires", dtf.resolvedOptions().timeZone);
+