fix signed/unsigned mismatch on Windows

Author: vaintroub

storage/innobase/srv/srv0srv.cc

@@ -2589,8 +2589,8 @@ DECLARE_THREAD(srv_worker_thread)(
 	slot = srv_reserve_slot(SRV_WORKER);
 
 	ut_a(srv_n_purge_threads > 1);
-	ut_a(my_atomic_loadlint(&srv_sys.n_threads_active[SRV_WORKER])
-	     < static_cast<lint>(srv_n_purge_threads));
+	ut_a(ulong(my_atomic_loadlint(&srv_sys.n_threads_active[SRV_WORKER]))
+	     < srv_n_purge_threads);
 
 	/* We need to ensure that the worker threads exit after the
 	purge coordinator thread. Otherwise the purge coordinator can