Change the isc_statscounter_t type from int to C99 int_fast64_t type

For TCP high-water work, we need to keep the used integer types widths
in sync.

Note: int_fast32_t is used on WIN32 platform

lib/isc/include/isc/types.h

@@ -72,7 +72,11 @@ typedef struct isc_socket		isc_socket_t;		/*%< Socket */
 typedef struct isc_socketevent		isc_socketevent_t;	/*%< Socket Event */
 typedef struct isc_socketmgr		isc_socketmgr_t;	/*%< Socket Manager */
 typedef struct isc_stats		isc_stats_t;		/*%< Statistics */
-typedef int				isc_statscounter_t;	/*%< Statistics Counter */
+#if defined(_WIN32) && !defined(_WIN64)
+	typedef int_fast32_t 		isc_statscounter_t;	/*%< Statistics Counter */
+#else
+	typedef int_fast64_t 		isc_statscounter_t;
+#endif
 typedef struct isc_symtab		isc_symtab_t;		/*%< Symbol Table */
 typedef struct isc_task			isc_task_t;		/*%< Task */
 typedef ISC_LIST(isc_task_t)		isc_tasklist_t;		/*%< Task List */