'undefined' is not literal, so dump it as identifier.

src/libjsparser/lexer.c

@@ -464,10 +464,6 @@ decode_keyword (void)
       return convert_current_token_to_token (TOK_NAME);
     }
   }
-  if (current_token_equals_to ("undefined"))
-  {
-    return create_token (TOK_UNDEFINED, 0);
-  }
   return empty_token;
 }
 
@@ -1416,7 +1412,6 @@ lexer_token_type_to_string (token_type tt)
 
     case TOK_DIV: return "/";
     case TOK_DIV_EQ: return "/=";
-    case TOK_UNDEFINED: return "undefined";
     default: JERRY_UNREACHABLE ();
   }
 }

src/libjsparser/lexer.h

@@ -131,7 +131,6 @@ typedef enum
 
   TOK_DIV, // /
   TOK_DIV_EQ, // /=
-  TOK_UNDEFINED, // undefined
   TOK_EMPTY,
 }
 token_type;

src/libjsparser/parser.c

@@ -1610,12 +1610,6 @@ parse_primary_expression (void)
       STACK_PUSH (IDX, token_data ());
       break;
     }
-    case TOK_UNDEFINED:
-    {
-      STACK_PUSH (IDX, next_temp_name ());
-      DUMP_OPCODE_3 (assignment, ID(1), OPCODE_ARG_TYPE_SIMPLE, ECMA_SIMPLE_VALUE_UNDEFINED);
-      break;
-    }
     case TOK_NULL:
     case TOK_BOOL:
     case TOK_SMALL_INT: