mod_http_muc_log: Remove dead code This might be something left over since a different variant where the loop went like `for n = i-1, i-100, -1 do ... end` i.e. it went trough a fixed number of items instead of all the page until the current message. Then it would have needed something to stop going over the end, but since the checks are simple it shouldn't be much of a problem looping over even a very busy day.

Generate a DNS UPDATE order in format suitable for `nsupdate` based on
current port configuration.

Example output:

```
$ prosodyctl mod_dnsupdate -d example.com -t xmpp.example.com example.com
zone example.com
server ns1.example.com
ttl 3600
add _xmpp-client._tcp.example.com IN SRV 1 1 5222
add _xmpp-server._tcp.example.com IN SRV 1 1 5269
```