Fix un-initialised "used" field in --listen-address structure.

Also remove unused "isloop" field.

src/dnsmasq.h

@@ -425,7 +425,7 @@ struct listener {
 struct iname {
   char *name;
   union mysockaddr addr;
-  int isloop, used;
+  int used;
   struct iname *next;
 };