Fix a C compiler warning about an implicitly reduced integer range (Py_ssize_t...

Fix a C compiler warning about an implicitly reduced integer range (Py_ssize_t -> int) when calling a helper function.
Closes GH-3028.

Cython/Utility/ObjectHandling.c

@@ -2021,7 +2021,7 @@ static CYTHON_INLINE PyObject* __Pyx_PyObject_CallMethO(PyObject *func, PyObject
 #define __Pyx_PyFunction_FastCall(func, args, nargs) \
     __Pyx_PyFunction_FastCallDict((func), (args), (nargs), NULL)
 
-static PyObject *__Pyx_PyFunction_FastCallDict(PyObject *func, PyObject **args, int nargs, PyObject *kwargs);
+static PyObject *__Pyx_PyFunction_FastCallDict(PyObject *func, PyObject **args, Py_ssize_t nargs, PyObject *kwargs);
 #endif
 
 // Backport from Python 3
@@ -2098,7 +2098,7 @@ static PyObject* __Pyx_PyFunction_FastCallNoKw(PyCodeObject *co, PyObject **args
 }
 
 
-static PyObject *__Pyx_PyFunction_FastCallDict(PyObject *func, PyObject **args, int nargs, PyObject *kwargs) {
+static PyObject *__Pyx_PyFunction_FastCallDict(PyObject *func, PyObject **args, Py_ssize_t nargs, PyObject *kwargs) {
     PyCodeObject *co = (PyCodeObject *)PyFunction_GET_CODE(func);
     PyObject *globals = PyFunction_GET_GLOBALS(func);
     PyObject *argdefs = PyFunction_GET_DEFAULTS(func);