cleanup: use Server::ischannel and Server::send_message

```
Code cleanup:
 - Server::ischannel can be used to identify if a received message is from
a channel.
 - Server::send_message is better than inserting /msg commands.
```

Original issue reported on code.google.com by `tristan....@gmail.com` on 21 Nov 2006 at 5:22
