Move Include/longobject.h non-limited API to a new
Include/cpython/longobject.h header file.
Move the following definitions to the internal C API:
* _PyLong_DigitValue
* _PyLong_FormatAdvancedWriter()
* _PyLong_FormatWriter()
Reorganize pycore_interp_init() to initialize singletons before the
the first PyType_Ready() call. Fix an issue when Python is configured
using --without-doc-strings.
Replace _PyThreadState_GET() with _PyInterpreterState_GET() in
functions which only need the current interpreter, but don't need the
current Python thread state.
Replace also _PyThreadState_UncheckedGet() with _PyThreadState_GET()
in faulthandler.c, since _PyThreadState_UncheckedGet() is just an
alias to _PyThreadState_GET() in practice.
Add _PyLong_GetZero() and _PyLong_GetOne() functions and a new
internal pycore_long.h header file.
Python cannot be built without small integer singletons anymore.