Use Py_hash_t type in Python3; should fix Python3 hash tests.

dulwich/_diff_tree.c

@@ -25,6 +25,10 @@
 typedef unsigned short mode_t;
 #endif
 
+#if PY_MAJOR_VERSION < 3
+typedef long Py_hash_t;
+#endif
+
 #if PY_MAJOR_VERSION >= 3
 #define PyInt_FromLong PyLong_FromLong
 #define PyInt_AsLong PyLong_AsLong
@@ -292,11 +296,11 @@ static PyObject *py_is_tree(PyObject *self, PyObject *args)
 	return result;
 }
 
-static int add_hash(PyObject *get, PyObject *set, char *str, int n)
+static Py_hash_t add_hash(PyObject *get, PyObject *set, char *str, int n)
 {
 	PyObject *str_obj = NULL, *hash_obj = NULL, *value = NULL,
 		*set_value = NULL;
-	long hash;
+	Py_hash_t hash;
 
 	/* It would be nice to hash without copying str into a PyString, but that
 	 * isn't exposed by the API. */