Fix type.

src/sys_tree.c

@@ -26,6 +26,7 @@ Contributors:
 
 #include "mosquitto_broker_internal.h"
 #include "memory_mosq.h"
+#include "sys_tree.h"
 #include "time_mosq.h"
 
 #define BUFLEN 100

src/sys_tree.h

@@ -29,7 +29,7 @@ extern unsigned long g_msgs_sent;
 extern unsigned long g_pub_msgs_received;
 extern unsigned long g_pub_msgs_sent;
 extern unsigned long g_msgs_dropped;
-extern int g_clients_expired;
+extern unsigned int g_clients_expired;
 extern unsigned int g_socket_connections;
 extern unsigned int g_connection_count;