Implement ES2015 class feature (part II.) (#2439)

This patch is the second milestone of the implementation of this new language element.

Supported:
 - Single class inheritance
 - Functionality of 'super' keyword
 - Implicit constructor in class heritage
 - Specific behaviour while extending with the built-in 'Array' or '%TypedArray%' object
 - Abstract subclasses (Mix-ins)

JerryScript-DCO-1.0-Signed-off-by: Robert Fancsik frobert@inf.u-szeged.hu

tests/jerry/es2015/class-inheritance-core-14.js

@@ -0,0 +1,53 @@
+/* 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.
+ */
+
+class A {
+  constructor () {
+    this.a = 5;
+  }
+
+  f () {
+    return 10;
+  }
+
+  super () {
+    this.super = 10;
+    return 15;
+  }
+}
+
+class B extends A {
+  constructor () {
+    super ();
+    assert (super.f === A.prototype.f);
+    super.f = 8;
+    assert (this.f === 8);
+    assert (super.f === A.prototype.f);
+
+    assert (this.a === 5);
+    super.a = 10;
+    assert (this.a === 10);
+
+    assert (super.super () === 15);
+    assert (this.super === 10);
+    super.super = 20;
+    assert (this.super === 20);
+    assert (super.super () === 15);
+  }
+}
+
+var b = new B;
+assert (b.f === 8);
+assert (b.a === 10);