fsmonitor: incorporate fixes for Python 3.10 (issue6612)

Differential Revision: https://phab.mercurial-scm.org/D11862

hgext/fsmonitor/pywatchman/bser.c

@@ -28,6 +28,7 b' OR TORT (INCLUDING NEGLIGENCE OR OTHERWI'
 OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
 
+#define PY_SSIZE_T_CLEAN
 #include <Python.h>
 #include <bytesobject.h>
 #ifdef _MSC_VER
@@ -1052,7 +1053,7 b' static int pdu_info_helper('
     int64_t* total_len_out) {
   const char* start = NULL;
   const char* data = NULL;
-  int datalen = 0;
+  Py_ssize_t datalen = 0;
   const char* end;
   int64_t expected_len;
   off_t position;
@@ -1101,7 +1102,7 b' static PyObject* bser_pdu_len(PyObject* '
 
 static PyObject* bser_loads(PyObject* self, PyObject* args, PyObject* kw) {
   const char* data = NULL;
-  int datalen = 0;
+  Py_ssize_t datalen = 0;
   const char* start;
   const char* end;
   int64_t expected_len;