fix build when int64 atomics are not lock-free

include/libtorrent/performance_counters.hpp

@@ -33,6 +33,9 @@ POSSIBILITY OF SUCH DAMAGE.
 #ifndef TORRENT_PERFORMANCE_COUNTERS_HPP_INCLUDED
 #define TORRENT_PERFORMANCE_COUNTERS_HPP_INCLUDED
 
+#include "libtorrent/config.hpp"
+#include "libtorrent/thread.hpp"
+
 #include "libtorrent/aux_/disable_warnings_push.hpp"
 
 #include <boost/cstdint.hpp>
@@ -40,8 +43,6 @@ POSSIBILITY OF SUCH DAMAGE.
 
 #include "libtorrent/aux_/disable_warnings_pop.hpp"
 
-#include "libtorrent/config.hpp"
-
 namespace libtorrent
 {
 	struct TORRENT_EXTRA_EXPORT counters