Fixes and improvements
- RTSP server: write UDP packets in parallel. This increases bandwidth and prevents freezes caused by lagging readers.
- RTSP server: log error if config parsing fails
- RTSP server, rtsp source: send receiver reports only after receiving a sender report
- RTSP source: send receiver reports even with sourceAnyPortEnable (#698)
- RTSP source: set ServerName when using TLS (#708)
- HLS: correctly compute segment duration