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

@@ -1933,7 +1933,7 @@ static CYTHON_INLINE PyObject* __Pyx_PyObject_CallMethO(PyObject *func, PyObject
 
 // let's assume that the non-public C-API function might still change during the 3.6 beta phase
 #if 1 || PY_VERSION_HEX < 0x030600B1
-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);
 #else
 #define __Pyx_PyFunction_FastCallDict(func, args, nargs, kwargs) _PyFunction_FastCallDict(func, args, nargs, kwargs)
 #endif
@@ -2014,7 +2014,7 @@ static PyObject* __Pyx_PyFunction_FastCallNoKw(PyCodeObject *co, PyObject **args
 
 
 #if 1 || PY_VERSION_HEX < 0x030600B1
-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);
@@ -2108,12 +2108,12 @@ static PyObject *__Pyx_PyFunction_FastCallDict(PyObject *func, PyObject **args,
     //#elif PY_MAJOR_VERSION >= 3
 #if PY_MAJOR_VERSION >= 3
     result = PyEval_EvalCodeEx((PyObject*)co, globals, (PyObject *)NULL,
-                               args, nargs,
+                               args, (int)nargs,
                                k, (int)nk,
                                d, (int)nd, kwdefs, closure);
 #else
     result = PyEval_EvalCodeEx(co, globals, (PyObject *)NULL,
-                               args, nargs,
+                               args, (int)nargs,
                                k, (int)nk,
                                d, (int)nd, closure);
 #endif