Use Py_ssize_t for PySet_Size() like all the other Py*_Size() functions.

Include/setobject.h

@@ -76,7 +76,7 @@ PyAPI_DATA(PyTypeObject) PyFrozenSet_Type;
 
 PyAPI_FUNC(PyObject *) PySet_New(PyObject *);
 PyAPI_FUNC(PyObject *) PyFrozenSet_New(PyObject *);
-PyAPI_FUNC(int) PySet_Size(PyObject *anyset);
+PyAPI_FUNC(Py_ssize_t) PySet_Size(PyObject *anyset);
 #define PySet_GET_SIZE(so) (((PySetObject *)(so))->used)
 PyAPI_FUNC(int) PySet_Contains(PyObject *anyset, PyObject *key);
 PyAPI_FUNC(int) PySet_Discard(PyObject *set, PyObject *key);

Objects/setobject.c

@@ -1958,7 +1958,7 @@ PyFrozenSet_New(PyObject *iterable)
 	return result;
 }
 
-int
+Py_ssize_t
 PySet_Size(PyObject *anyset)
 {
 	if (!PyAnySet_Check(anyset)) {