Apply IP filters to address reported via Telnet Location command

Feature requested (?) by u/jumbotronjim on https://www.reddit.com/r/synchronet/:

If the client connection is from a blocked IP address (in ip[-silent].can), but still manages to get through the web server and websocketservice and have their correct IP address reported via Telnet Location, terminate the connection. Seems dubious.

src/sbbs3/answer.cpp

 /* Synchronet answer "caller" function */
-// vi: tabstop=4
-
-/* $Id: answer.cpp,v 1.116 2020/08/02 03:37:24 rswindell Exp $ */
 
 /****************************************************************************
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@@ -16,21 +13,9 @@
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@@ -436,6 +421,16 @@ bool sbbs_t::answer()
 			} else {
 				if(telnet_location[0]) {			/* Telnet Location info provided */
 					lprintf(LOG_INFO, "Telnet Location: %s", telnet_location);
+					if(trashcan(telnet_location, "ip-silent")) {
+						hangup();
+						return false;
+					}
+					if(trashcan(telnet_location, "ip")) {
+						lprintf(LOG_NOTICE, "%04d %s !TELNET LOCATION BLOCKED in ip.can: %s"
+							,client_socket, client.protocol, telnet_location);
+						hangup();
+						return false;
+					}
 					SAFECOPY(cid, telnet_location);
 				}
 			}