Initial implementation of class fields (#4191)

Missing features:
 - this binding in static fields are not supported
 - static field evaluation order is wrong
 - function names are not supported

JerryScript-DCO-1.0-Signed-off-by: Zoltan Herczeg zherczeg.u-szeged@partner.samsung.com

tests/jerry/es.next/class-fields3.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.
+
+function check_property(obj, name, value)
+{
+  property = Object.getOwnPropertyDescriptor(obj, name)
+  assert(typeof property === "object")
+  assert(property.value === value)
+}
+
+var o = {}
+var name = "Pro"
+var res = 0
+var counter = 0
+
+function f1() {
+  counter++
+}
+
+class C1 {
+  static
+    v\u0061r
+  static Prop =
+    res
+    =
+    "msg"
+  static
+    Prop
+    =
+    f1()
+  static [name + "p"] = (f1(), o)
+  static 22 = 3 * 4  ;static 23 = 5 + 6
+  static 'a b'
+}
+
+check_property(C1, "var", undefined)
+check_property(C1, "Prop", o)
+check_property(C1, 22, 12)
+check_property(C1, 23, 11)
+check_property(C1, "a b", undefined)
+assert(res === "msg")
+assert(counter === 2)