Web request part of supernode resync (not quite done, needs test)

node/Constants.hpp

@@ -409,6 +409,13 @@
  */
 #define ZT_UPDATE_HTTP_TIMEOUT 120
 
+/**
+ * Delay between fetches of the root topology update URL
+ *
+ * 86400000 = check once every 24 hours (this doesn't change often)
+ */
+#define ZT_UPDATE_ROOT_TOPOLOGY_CHECK_INTERVAL 86400000
+
 /**
  * Sanity limit on maximum bridge routes
  *