Re-target for ES.Next (#3901)

A list of changes:
- 'es2015-subset' profile is deprecated, and an 'es.next' profile is added.
- The default profile is changed to 'es.next'
- Renamed the JERRY_ES2015 guard to JERRY_ESNEXT
- Renamed JERRY_ES2015_BUILTIN_* guards to JERRY_BUILTIN_*
- Moved es2015 specific tests to a new 'es.next' subdirectory
- Updated docs, targets, and test runners to reflect these changes

Resolves #3737.

JerryScript-DCO-1.0-Signed-off-by: Dániel Bátyai dbatyai@inf.u-szeged.hu

tests/jerry/es.next/let3.js

@@ -0,0 +1,87 @@
+/* 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 g = -1;
+
+function f1() {
+  /* Function copied to var. */
+  assert (g === undefined);
+
+  {
+    assert (g() === 1);
+    function g() { return 1 };
+
+    {
+      assert (g() === 2);
+      function g() { return 2 };
+    }
+
+    assert (g() === 1);
+  }
+
+  assert (g() === 2);
+}
+f1();
+
+function f2() {
+  /* Function is not copied to var. */
+  'use strict'
+  assert (g === -1);
+
+  {
+    assert (g() === 1);
+    function g() { return 1 };
+
+    {
+      assert (g() === 2);
+      function g() { return 2 };
+    }
+
+    assert (g() === 1);
+  }
+
+  assert (g === -1);
+}
+f2();
+
+function f3() {
+  /* Function hoisted as let. */
+  assert (g === -1);
+
+  {
+    let g = 1;
+
+    {
+      if (true)
+      {
+        assert (g() === 2);
+
+        if (true)
+        {
+          assert (g() === 2);
+        }
+
+        function g() { return 2 };
+      }
+
+      assert (g === 1);
+    }
+
+    assert (g === 1);
+  }
+
+  assert (g === -1);
+}
+f3();