Rework error to use a global slot to store the error value.

This change frees up the error bit in ecma_value_t, which allows
to define 4 more value types (e.g. symbols). To keep API
compatibility we introduce a box for values with error flag.

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

jerry-core/api/jerry-snapshot.c

@@ -534,7 +534,7 @@ jerry_parse_and_save_snapshot_with_args (const jerry_char_t *source_p, /**< scri
 
   if (ECMA_IS_VALUE_ERROR (parse_status))
   {
-    ecma_free_value (parse_status);
+    ecma_free_value (JERRY_CONTEXT (error_value));
     return 0;
   }
 
@@ -728,6 +728,11 @@ jerry_snapshot_result_at (const uint32_t *snapshot_p, /**< snapshot */
     ecma_bytecode_deref (bytecode_p);
   }
 
+  if (ECMA_IS_VALUE_ERROR (ret_val))
+  {
+    return ecma_create_error_reference (JERRY_CONTEXT (error_value));
+  }
+
   return ret_val;
 } /* jerry_snapshot_result_at */
 #endif /* JERRY_ENABLE_SNAPSHOT_EXEC */
@@ -1312,14 +1317,14 @@ jerry_parse_and_save_literals (const jerry_char_t *source_p, /**< script source
                                       is_strict,
                                       &bytecode_data_p);
 
-  const bool error = ECMA_IS_VALUE_ERROR (parse_status);
-  ecma_free_value (parse_status);
-
-  if (error)
+  if (ECMA_IS_VALUE_ERROR (parse_status))
   {
+    ecma_free_value (JERRY_CONTEXT (error_value));
     return 0;
   }
 
+  ecma_free_value (parse_status);
+
   ecma_bytecode_deref (bytecode_data_p);
 
   ecma_lit_storage_item_t *string_list_p = JERRY_CONTEXT (string_list_first_p);