Update net/gst-rtsp-server to 1.19.2

[Matthias Petermann <mp%petermann-it.de@localhost>]

Hello all,

I have staged an update for gst-rtsp-server in wip[1]. Would anyone like 
to assess this and import it into pkgsrc if possible? I'd like to see 
the new version because I need it as a dependency for a Rust package. 
Details are in the COMMIT_MSG.

Thanks & many greetings
Matthias

[1] 
https://wip.pkgsrc.org/cgi-bin/gitweb.cgi?p=pkgsrc-wip.git;a=tree;f=gst-rtsp-server;h=0766bc8c397a8a794782290714af98f784abf6db;hb=HEAD