Remove PyGen_NeedsFinalizing(): it was not
documented, tested or used anywhere within CPython after
the implementation of PEP 442.

* Rename PyThreadState_DeleteCurrent()
  to _PyThreadState_DeleteCurrent()
* Move it to the internal C API

Co-Authored-By: Carol Willing <carolcode@willingconsulting.com>

MSVC 2015 supports %zd / %zu.  "z" is portable enough nowadays.

Declare Py_BytesMain() in Include/pylifecycle.h, rather in
Include/internal/pycore_pylifecycle.h.

For example, rename PyTuple_Fini() to _PyTuple_Fini().

These functions are only declared in the internal C API.

- drop TargetScopeError in favour of raising SyntaxError directly
  as per the updated PEP 572
- comprehension iteration variables are explicitly local, but
  named expression targets in comprehensions are nonlocal or
  global. Raise SyntaxError as specified in PEP 572
- named expression targets in the outermost iterable of a
  comprehension have an ambiguous target scope. Avoid resolving
  that question now by raising SyntaxError. PEP 572
  originally required this only for cases where the bound name
  conflicts with the iteration variable in the comprehension,
  but CPython can't easily restrict the exception to that case
  (as it doesn't know the target variable names when visiting
  the outermost iterator expression)

Fix assert statement misbehavior if AssertionError is shadowed.

PyConfig_Read() is now responsible to handle early calls to
PySys_AddXOption() and PySys_AddWarnOption().

Options added by PySys_AddXOption() are now handled the same way than
PyConfig.xoptions and command line -X options.

For example, PySys_AddXOption(L"faulthandler") enables faulthandler
as expected.