fix #769

Add 379 RPL_WHOISMODES

irc/numerics.go

 	RPL_ENDOFINFO                 = "374"
 	RPL_MOTDSTART                 = "375"
 	RPL_ENDOFMOTD                 = "376"
+	RPL_WHOISMODES                = "379"
 	RPL_YOUREOPER                 = "381"
 	RPL_REHASHING                 = "382"
 	RPL_YOURESERVICE              = "383"

irc/server.go

 	}
 	if client == target || hasPrivs {
 		rb.Add(nil, client.server.name, RPL_WHOISACTUALLY, cnick, tnick, fmt.Sprintf("%s@%s", targetInfo.username, target.RawHostname()), target.IPString(), client.t("Actual user@host, Actual IP"))
+		rb.Add(nil, client.server.name, RPL_WHOISMODES, cnick, tnick, fmt.Sprintf(client.t("is using modes +%s"), target.modes.String()))
 	}
 	if target.HasMode(modes.TLS) {
 		rb.Add(nil, client.server.name, RPL_WHOISSECURE, cnick, tnick, client.t("is using a secure connection"))