Backport METH_FASTCALL from Python 3.7 (#328)

third_party/python/Include/methodobject.h

@@ -14,10 +14,12 @@ extern PyTypeObject PyCFunction_Type;
 #define PyCFunction_Check(op) (Py_TYPE(op) == &PyCFunction_Type)
 
 typedef PyObject *(*PyCFunction)(PyObject *, PyObject *);
-typedef PyObject *(*_PyCFunctionFast) (PyObject *self, PyObject **args,
-                                       Py_ssize_t nargs, PyObject *kwnames);
+typedef PyObject *(*_PyCFunctionFast) (PyObject *, PyObject **, Py_ssize_t);
 typedef PyObject *(*PyCFunctionWithKeywords)(PyObject *, PyObject *,
                                              PyObject *);
+typedef PyObject *(*_PyCFunctionFastWithKeywords) (PyObject *,
+                                                   PyObject **, Py_ssize_t,
+                                                   PyObject *);
 typedef PyObject *(*PyNoArgsFunction)(PyObject *);
 
 PyCFunction PyCFunction_GetFunction(PyObject *);
@@ -93,12 +95,20 @@ typedef struct {
     PyObject    *m_module; /* The __module__ attribute, can be anything */
     PyObject    *m_weakreflist; /* List of weak references */
 } PyCFunctionObject;
+
 PyObject * _PyMethodDef_RawFastCallDict(
     PyMethodDef *method,
     PyObject *self,
     PyObject **args,
     Py_ssize_t nargs,
     PyObject *kwargs);
+
+PyObject * _PyMethodDef_RawFastCallKeywords(
+    PyMethodDef *method,
+    PyObject *self,
+    PyObject **args,
+    Py_ssize_t nargs,
+    PyObject *kwnames);
 #endif
 
 int PyCFunction_ClearFreeList(void);