Implement Object.isExtensible and Object.preventExtensions function

JerryScript-DCO-1.0-Signed-off-by: Kristof Kosztyo kkosztyo.u-szeged@partner.samsung.com

tests/jerry/object_is_extensible.js

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+// Copyright 2015 Samsung Electronics Co., Ltd.
+// Copyright 2015 University of Szeged.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// New objects are extensible.
+var empty = {};
+assert (Object.isExtensible(empty) === true);
+
+// ...but that can be changed.
+Object.preventExtensions(empty);
+assert(Object.isExtensible(empty) === false);
+
+// Call on undefined should throw TypeError.
+try
+{
+    Object.isExtensible(undefined);
+    assert (false);
+} catch (e) {
+    assert (e instanceof TypeError);
+}
+
+try
+{
+    Object.preventExtensions(undefined);
+    assert (false);
+} catch (e) {
+    assert (e instanceof TypeError);
+}
+
+// The functions below are unimplemented.
+// Sealed objects are by definition non-extensible.
+// var sealed = Object.seal({});
+// assert(Object.isExtensible(sealed) === false);
+
+// Frozen objects are also by definition non-extensible.
+// var frozen = Object.freeze({});
+// assert(Object.isExtensible(frozen) === false);