Add literals - replacements of strings and numbers in parser.

tests/jerry/object_literal-2.js

@@ -14,4 +14,13 @@
 
 var a = {get a(){return undefined}, set a(b){}}
 
-// var b = {if:0, else:1, try:2, catch:3, finally:4}
+var b = {if:0, else:1, try:2, catch:3, finally:4, let:5}
+
+assert (b.if + b.else + b.try + b.catch + b.finally + b.let === 15)
+
+function c() {
+  "use strict"
+  var b = {let:15, enum:10}
+  assert (b.let + b.enum === 25)
+}
+c();