Enforce a message size limit

Forces all messages to be at most 512 bytes, to stop 'cmd help all' from irc_commands DoSing the server.
This is done in the core IRC mod so it limits everything rather than just irc_commands.

init.lua

@@ -213,6 +213,5 @@ end
 
 function irc.queue(msg)
 	if not irc.connected then return end
-	irc.conn:queue(msg)
+	irc.conn:queue(msg:sub(1, 512))
 end
-