Implement Cyclops subject modification for exported messages if

"subject_mod = true" in the listserver.ini for the particular list
(default = false).

exec/listserver.js

@@ -294,6 +294,8 @@ for(var l in list_array) {
 
 		hdr.replyto_net_type = NET_INTERNET;
 		hdr.replyto_net_addr = list.address;
+		if(list.subject_mod==true)
+			hdr.subject = "[" + list.name + "] " + hdr.subject;
 		if(!mailbase.save_msg(hdr,body,rcpt_list))
 			log(LOG_ERR,format("ListServer: %s !ERROR %s saving mail message"
 				,list.name, mailbase.error));