* The header files have been reorganized to better separate the different kinds

of APIs:

* ``Include/*.h`` should be the portable public stable C API.

* ``Include/cpython/*.h`` should be the unstable C API specific to CPython;

public API, with some private API prefixed by ``_Py`` or ``_PY``.

* ``Include/internal/*.h`` is the private internal C API very specific to

CPython. This API comes with no backward compatibility warranty and should

not be used outside CPython. It is only exposed for very specific needs

like debuggers and profiles which has to access to CPython internals

without calling functions. This API is now installed by ``make install``.

(Contributed by Victor Stinner in :issue:`35134` and :issue:`35081`,

work initiated by Eric Snow in Python 3.7)

* Some macros have been converted to static inline functions: parameter types

and return type are well defined, they don't have issues specific to macros,

variables have a local scopes. Examples:

* :c:func:`Py_INCREF`, :c:func:`Py_DECREF`

* :c:func:`Py_XINCREF`, :c:func:`Py_XDECREF`

* :c:func:`PyObject_INIT`, :c:func:`PyObject_INIT_VAR`

* Private functions: :c:func:`_PyObject_GC_TRACK`,

:c:func:`_PyObject_GC_UNTRACK`, :c:func:`_Py_Dealloc`

(Contributed by Victor Stinner in :issue:`35059`.)