Implement Symbol.unscopables (#3405)

Added a new property for Array.prototype based on ECMA-262 v6, 22.1.3.31
Also upgraded the HasBinding operation with ECMA-262 v6, 8.1.1.2.1 steps 7-9

JerryScript-DCO-1.0-Signed-off-by: Adam Szilagyi aszilagy@inf.u-szeged.hu

tests/jerry/es2015/symbol-unscopables.js

@@ -0,0 +1,88 @@
+// Copyright JS Foundation and other contributors, http://js.foundation
+//
+// 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.
+
+var obj = {
+    prop1: 42,
+    prop2: 13,
+    prop3: "foo",
+    prop4: 1
+};
+
+var obj2 = {
+    foo: "foo"
+};
+
+obj[Symbol.unscopables] = {
+    prop1: false,
+    prop2: true,
+    prop3: undefined,
+    prop4: obj2
+};
+
+with (obj)
+{
+    assert(prop1 === 42);
+
+    try {
+      prop2;
+      assert(false);
+    } catch (e) {
+      assert(e instanceof ReferenceError);
+    }
+
+    assert (prop3 === "foo");
+
+    try {
+      prop4;
+      assert(false);
+    } catch (e) {
+      assert(e instanceof ReferenceError);
+    }
+
+    try {
+      prop5;
+      assert(false);
+    } catch (e) {
+      assert(e instanceof ReferenceError);
+    }
+}
+
+var obj2 = {};
+Object.defineProperty(obj2, Symbol.unscopables, { get: function () { throw 42; } });
+
+with (obj2) {
+  try {
+    prop;
+    assert(false);
+  } catch (e) {
+    assert(e instanceof ReferenceError);
+  }
+}
+
+var symbol_obj = Array.prototype[Symbol.unscopables];
+assert(symbol_obj.copyWithin === true);
+assert(symbol_obj.entries === true);
+assert(symbol_obj.fill === true);
+assert(symbol_obj.find === true);
+assert(symbol_obj.findIndex === true);
+assert(symbol_obj.keys === true);
+assert(symbol_obj.values === true);
+
+assert(Object.getPrototypeOf(Array.prototype[Symbol.unscopables]) === null);
+
+var obj3 = Object.getOwnPropertyDescriptor(Array.prototype[Symbol.unscopables], "find");
+assert(obj3.value === true);
+assert(obj3.writable === true);
+assert(obj3.enumerable == true);
+assert(obj3.configurable == true);