Add RateLimiter for rate limiting multicast, not tested yet.

node/Constants.hpp

@@ -266,6 +266,21 @@ error_no_ZT_ARCH_defined;
  */
 #define ZT_MULTICAST_LOCAL_POLL_PERIOD 10000
 
+/**
+ * Default bytes per second limit for multicasts per peer on a network
+ */
+#define ZT_MULTICAST_DEFAULT_BYTES_PER_SECOND 50.0
+
+/**
+ * Default balance preload for multicast rate limiters on a network
+ */
+#define ZT_MULTICAST_DEFAULT_RATE_PRELOAD 25.0
+
+/**
+ * Absolute maximum balance for multicast rate limiters
+ */
+#define ZT_MULTICAST_DEFAULT_RATE_MAX 75.0
+
 /**
  * Delay between scans of the topology active peer DB for peers that need ping
  */