_Py_CheckRecursionLimit variable is no longer needed and can be removed.

In Python 3.9, I added a recursion limit per interpreter.

In Python 3.8 and older, it was used by _Py_MakeRecCheck() macro to check for recursion error.

Previously, the _Py_CheckRecursionLimit variable was kept for backward compatibility with the stable ABI, but in Python 3.8 and older, Py_EnterRecursiveCall() and Py_LeaveRecursiveCall() could not be used with the limited C API since these macros accessed PyThreadState structure member, whereas the structure is opaque in the limited C API.

Attached PR removed the variable.

---

(3) bpo-40513: Limit made per interpreter.

commit 4e30ed3
Author: Victor Stinner <vstinner@python.org>
Date: Tue May 5 16:52:52 2020 +0200

bpo-40513: Per-interpreter recursion_limit (GH-19929)

Move recursion_limit member from _PyRuntimeState.ceval to
PyInterpreterState.ceval.

* Py_SetRecursionLimit() now only sets _Py_CheckRecursionLimit
  of ceval.c if the current Python thread is part of the main
  interpreter.
* Inline _Py_MakeEndRecCheck() into _Py_LeaveRecursiveCall().
* Convert _Py_RecursionLimitLowerWaterMark() macro into a static
  inline function.

---

(2) bpo-38644: The _Py_CheckRecursionLimit variable was used by Py_EnterRecursiveCall() and Py_LeaveRecursiveCall() macros. I converted these macros into function calls in Python 3.9:

commit f4b1e3d
Author: Victor Stinner <vstinner@python.org>
Date: Mon Nov 4 19:48:34 2019 +0100

bpo-38644: Add Py_EnterRecursiveCall() to the limited API (GH-17046)

Provide Py_EnterRecursiveCall() and Py_LeaveRecursiveCall() as
regular functions for the limited API. Previously, there were defined
as macros, but these macros didn't work with the limited API which
cannot access PyThreadState.recursion_depth field.

Remove _Py_CheckRecursionLimit from the stable ABI.

Add [Include/cpython/ceval.h](https://github.com/python/cpython/blob/main/Include/cpython/ceval.h) header file.

In pycore_ceval.h, the function is overriden by a macro which points to an inline function which uses:

• tstate->recursion_depth
• tstate->interp->ceval.recursion_limit
• tstate->stackcheck_counter (if USE_STACKCHECK macro is defined)

---

(1) bpo-31857: Original change adding the FIXME.

commit 1896793
Author: pdox <pdox@alum.mit.edu>
Date: Wed Oct 25 23:03:01 2017 -0700

bpo-31857: Make the behavior of USE_STACKCHECK deterministic (bpo-4098)

This change added the FIXME comment:

/* Due to the macros in which it's used, _Py_CheckRecursionLimit is in
the stable ABI. It should be removed therefrom when possible.
*/

New changeset 19c3ac9 by Victor Stinner in branch 'master':
bpo-41834: Remove _Py_CheckRecursionLimit variable (GH-22359)
19c3ac9