fptg 0.9.5

Call relay: a TURN server inside fptg-server on the HTTPS port

Calls when the client cannot reach Telegram itself (server on a VPS,
Telegram blocked on the client's network): the browser sends WebRTC media
only directly or through TURN, so the server relays it.

- turnrelay.pas: RFC 8656 subset - Allocate (UDP, IPv4), Refresh,
  CreatePermission, ChannelBind, Send/Data indications, ChannelData,
  Binding; long-term credentials with time-limited passwords
  (HMAC-SHA1 of a per-process secret).
- localserver: the first byte of a connection decides - TLS (0x16) or
  TURN over plain TCP, so the relay needs no extra port.
- webapi relay.get gives the page credentials; calls/relay.js uses the
  relay with iceTransportPolicy 'relay' for private calls and video chats.
  Settings -> Speakers and camera -> "Route calls through the server":
  Automatic (server on another computer), Always, Never.
- On by default in the console server, off in the server window;
  --no-relay, --relay-address=IP, --relay-ports=A-B, conf.dat [relay].
- README: calls through a VPS.