New minor features
- support external authentication (#504) (#517)
- make regexp groups available to custom commands (#642)
Fixes and improvements
- General: do not wait for external commands to exit during runtime
- General: print a message when a custom command exits suddently
- HLS, RTMP: compute duration correctly in case of an RTP overflow
- HLS, RTMP: fix DTS generation, avoid non-increasing DTS
- HLS: upgrade hls.js and enable progressive mode