ssdp: send a full byebye + alive set when a new interface comes online

If an interface comes online after startup, we really need to send a
complete byebye + alive set on that interface, but we don't want to do
it for other interfaces.  So do it as the interfaces come up, and
skip it for interfaces that existed before the reload.

upnpglobalvars.c

@@ -53,9 +53,6 @@
 #include "config.h"
 #include "upnpglobalvars.h"
 
-/* LAN address */
-/*const char * listen_addr = 0;*/
-
 /* startup time */
 time_t startup_time = 0;
 
@@ -78,6 +75,7 @@ char presentationurl[PRESENTATIONURL_MAX_LEN];
 
 int n_lan_addr = 0;
 struct lan_addr_s lan_addr[MAX_LAN_ADDR];
+int sssdp = -1;
 
 /* Path of the Unix socket used to communicate with MiniSSDPd */
 const char * minissdpdsocketpath = "/var/run/minissdpd.sock";