Support \u200C \u200D unicode characters (#3266)

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

tests/jerry/unicode-format-control-characters.js

@@ -0,0 +1,31 @@
+// 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.
+
+function checkSyntax (str) {
+  try {
+    eval (str);
+    assert (false);
+  } catch (e) {
+    assert (e instanceof SyntaxError);
+  }
+}
+
+// Only \u200C-Zero width non-joiner, and \u200D-Zero width joiner are allowed
+
+checkSyntax ("_\u200b\u200d");
+checkSyntax ("_\u200c\u200e");
+
+var _\u200c\u200d = 5;
+
+assert (_\u200c\u200d === 5);