Replace
   _PyObject_CallArg1(func, arg)
with
   PyObject_CallFunctionObjArgs(func, arg, NULL)

Using the _PyObject_CallArg1() macro increases the usage of the C stack, which
was unexpected and unwanted. PyObject_CallFunctionObjArgs() doesn't have this
issue.

Handling zero-argument super() in __init_subclass__ and
__set_name__ involved moving __class__ initialisation to
type.__new__. This requires cooperation from custom
metaclasses to ensure that the new __classcell__ entry
is passed along appropriately.

The initial implementation of that change resulted in abruptly
broken zero-argument super() support in metaclasses that didn't
adhere to the new requirements (such as Django's metaclass for
Model definitions).

The updated approach adopted here instead emits a deprecation
warning for those cases, and makes them work the same way they
did in Python 3.5.

This patch also improves the related class machinery documentation
to cover these details and to include more reader-friendly
cross-references and index entries.

Issue #28858: The change b9c9691c72c5 introduced a regression. It seems like
_PyObject_CallArg1() uses more stack memory than
PyObject_CallFunctionObjArgs().

names.

names.

names.

This is still useful for single source Python 2/3 code
migrating away from inspect.getargspec(), but that wasn't
clear with the documented deprecation in place.

Issue #28740: Add sys.getandroidapilevel(): return the build time
API version of Android as an integer.

Function only available on Android.

Replace
    PyObject_CallFunction(func, "O", arg)
and
    PyObject_CallFunction(func, "O", arg, NULL)
with
    _PyObject_CallArg1(func, arg)

Replace
    PyObject_CallFunction(func, NULL)
with
    _PyObject_CallNoArg(func)

_PyObject_CallNoArg() and _PyObject_CallArg1() are simpler and don't allocate
memory on the C stack.

Modify WITH_CLEANUP_START bytecode: replace PyObject_CallFunctionObjArgs() with
_PyObject_FastCall().

* PyObject_CallFunctionObjArgs(func, NULL) => _PyObject_CallNoArg(func)
* PyObject_CallFunctionObjArgs(func, arg, NULL) => _PyObject_CallArg1(func, arg)

PyObject_CallFunctionObjArgs() allocates 40 bytes on the C stack and requires
extra work to "parse" C arguments to build a C array of PyObject*.

_PyObject_CallNoArg() and _PyObject_CallArg1() are simpler and don't allocate
memory on the C stack.

This change is part of the fastcall project. The change on listsort() is
related to the issue #23507.

* Callable object: callable, o, callable_object => func
* Object for method calls: o => obj
* Method name: name or nameid => method

Cleanup also the C code:

* Don't initialize variables to NULL if they are not used before their first
  assignement
* Add braces for readability