Security: Disallow SSDP device discovery from non-local addresses.

Protection against MythTV's use in SSDP Reflection attacks.

https://www.prolexic.com/knowledge-center-ddos-threat-advisory-ssdp-reflection-ddos-attacks.html
https://www.prolexic.com/kcresources/prolexic-threat-advisories/prolexic-threat-advisory-ssdp-reflection-ddos-attacks/ssdp-reflection-attacks-cybersecurity-locked.html

No CVE assigned yet.
WebFrontend: Commit what I've got so far for the 'search list' feature. It's not yet finished, so there is no menu entry for it yet
Coverity: Fix overflow before assignment. ID 1229294
Coverity: Fix potential memory leaks on error (and false positives) in mythtranscode

ID 1025906
Coverity: Fix tiny leak if gif is not animated. ID 1248082
MythArchive: Move pxsup2data.* into an external/ subfolder to exclude it from Static Analysis checks
Fix compilation of mythfilerecorder with QT5.