xC: also force monospace for RPL_MOTDSTART

It tends to looks inconsistent without.

xC.c

@@ -8763,6 +8763,7 @@ irc_process_numeric (struct server *s,
 		if (msg->params.len == 2)
 			irc_try_parse_welcome_for_userhost (s, msg->params.vector[1]);
 		break;
+	case IRC_RPL_MOTDSTART:
 	case IRC_RPL_MOTD:
 		if (copy.len)
 			irc_adjust_motd (&copy.vector[0]);