Followed Steve's good recommendation, and made routed_get_my_address() be a variant of datalink_get_my_address() just when routing is in use. Haven't done anything about the sending functions yet.

Renamed Lookup_Routed_Device_Address() as Routed_Device_Address_Lookup(), and replaced it in the routed npdu handler with a function that finds the "next" gateway or routed device, as per the destination address.  (Less tied to the specifics of the gw_device.c implementation.)
Fixed a few build warnings (eg, %zu for size_t arguments).
Until we improve the makefile system, I've enabled BAC_ROUTING in config.h

bacnet-stack/demo/readfile/main.c

@@ -144,7 +144,7 @@ static void AtomicReadFileAckHandler(
                 } else if (octets_written == 0) {
                     fprintf(stderr, "Received 0 byte octet string!.\n");
                 } else {
-                    printf("\r%u bytes",
+                    printf("\r%zu bytes",
                         (data.type.stream.fileStartPosition + octets_written));
                 }
                 fflush(pFile);