Return self in GATHER requests if self is a member of multicast group, and reinstate legacy support.

node/Network.hpp

@@ -163,6 +163,16 @@ public:
 		return _myMulticastGroups;
 	}
 
+	/**
+	 * @param mg Multicast group
+	 * @return True if this network endpoint / peer is a member
+	 */
+	bool subscribedToMulticastGroup(const MulticastGroup &mg) const
+	{
+		Mutex::Lock _l(_lock);
+		return (_myMulticastGroups.find(mg) != _myMulticastGroups.end());
+	}
+
 	/**
 	 * Apply a NetworkConfig to this network
 	 *