IRC - add reputation block list (RBL) capability to synchronet irc

Recently we have had spam bots hammmer the various irc channels on the Synchronet irc service (irc.synchro.net).

Analysis of the source IP's of the bots show that in the most recent attack there was a perfect match for the IRC RBL known as dronebl (dronebl.org). See below for examples.

This request is to add the capability to utilise RBL service(s) including but not limited to drobebl to irc to help Synchronet sysop's combat the threat of their irc service being attacked by such bots.

It would be useful to include dronebl as the default RBL and allow the sysop to add additional ones as required.

---

Query: 152.180.149.193.dnsbl.dronebl.org A Record: 127.0.0.3 TTL: 300 DB_rc:

IRC Drone

TXT: 	

IRC spam drone (litmus/sdbot/fyle)

---

72.155.205.67.dnsbl.dronebl.org A Record: 127.0.0.3 TTL: 300 DB_rc:

IRC Drone

TXT: 	

IRC spam drone (litmus/sdbot/fyle)

---