Update to upstream release as of 2018.12.14

Details:

• Added support for sending (and handling) RTCP "BYE" packets that contain a 'reason' string.
• Fixed a bug in the server implementation of RTSP-over-HTTP to prevent a potential denial-of-service attack.
• Upstream changelog, see: http://www.live555.com/liveMedia/public/changelog.txt

MFH: 2018Q4