Support Unicode supplementary planes (#3928)

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

tests/jerry/es.next/unicode-escape-identifiers.js

@@ -0,0 +1,32 @@
+// 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 \u{102C0} = 2;
+assert(\u{102C0} === 2);
+
+var o1 = { \u{102C0} : 3 };
+assert(o1['\ud800\udec0'] === 3);
+
+var o2 = { '\ud800\udec0' : 4 };
+assert(o2.\u{102C0} === 4);
+
+try {
+  eval('var ⸯ');
+  assert(false);
+} catch(e) {
+  assert(e instanceof SyntaxError);
+}
+
+var 𐋀 = 5;
+assert(𐋀 === 5);