TIdTelnet needs to trigger OnDisconnect or OnStatus when disconnected

```
TIdTelnet uses an internal reading thread, and that thread does not trigger the 
OnDisconnect or OnStatus event when the thread terminates, such as due to an 
abnormal disconnect.
```

Original issue reported on code.google.com by `gambit47` on 15 Dec 2014 at 10:59
