net/coturn now usable on NetBSD -- try it if you've been wanting STUN/TURN

[Greg Troxel <gdt%lexort.com@localhost>]

(STUN is to discover one's public address.  TURN is a relay server used
mostly for VOIP and other media streams to work around firewalls and
NAT.  Both are in service of ICE -- Interactive Connection Establishment
-- to enable two nodes that might be afflicated with NAT and firewalls
to send UDP packets to each other, assuming they have control channel.)

"Keke" added wip/coturn in 2017 (!).  More recently, I updated it to the
most recent release, manu@ hoisted it to net/, and then I (not noticing)
improved wip and adam@ improved the net/ version.  I have just completed
a merge, which I think retains all of the improvements from both -- but
if not please email me and I'll look into it.

It runs as user/group coturn instead of root, so if you were avoiding it
because of that reason you may want to look again.

I believe that with this package installed and straightforwardly
configured per synapse's instructions, I have working matrix voice
calls.  (The trouble with NAT/firewall workarounds is that 
ICE might succeed anyway...)

Greg