changes since 1.2.15:
- send User-Agent field in anonymous mode
- fix python binding for settings_pack conversion
- fix DHT announce timer issue
- use DSCP_TRAFFIC_TYPE socket option on windows
- update default ToS setting according to RFC 8622
- keep trying to announce to trackers even when all fail
- don't disable announcing from local endpoints because of temporary failures
- fix issue in parsing UPnP XML response with multiple forwarding services