bpo-38644: Add _PyObject_Call() (GH-17089)

* Add pycore_call.h internal header file.
* Add _PyObject_Call(): PyObject_Call() with tstate
* Add _PyObject_CallNoArgTstate(): _PyObject_CallNoArg() with tstate
* Add _PyObject_FastCallDictTstate(): _PyObject_FastCallDict()
  with tstate
* _PyObject_Call_Prepend() now takes tstate
* Replace _PyObject_FastCall() calls
  with _PyObject_VectorcallTstate() calls

Include/internal/pycore_call.h

@@ -0,0 +1,39 @@
+#ifndef Py_INTERNAL_CALL_H
+#define Py_INTERNAL_CALL_H
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifndef Py_BUILD_CORE
+#  error "this header requires Py_BUILD_CORE define"
+#endif
+
+PyAPI_FUNC(PyObject *) _PyObject_Call_Prepend(
+    PyThreadState *tstate,
+    PyObject *callable,
+    PyObject *obj,
+    PyObject *args,
+    PyObject *kwargs);
+
+PyAPI_FUNC(PyObject *) _PyObject_FastCallDictTstate(
+    PyThreadState *tstate,
+    PyObject *callable,
+    PyObject *const *args,
+    size_t nargsf,
+    PyObject *kwargs);
+
+PyAPI_FUNC(PyObject *) _PyObject_Call(
+    PyThreadState *tstate,
+    PyObject *callable,
+    PyObject *args,
+    PyObject *kwargs);
+
+static inline PyObject *
+_PyObject_CallNoArgTstate(PyThreadState *tstate, PyObject *func) {
+    return _PyObject_VectorcallTstate(tstate, func, NULL, 0, NULL);
+}
+
+#ifdef __cplusplus
+}
+#endif
+#endif /* !Py_INTERNAL_CALL_H */