[docs] [issue32124] Document functions safe to be called before Py_Initialize()

[STINNER Victor]

New submission from STINNER Victor <victor.stinner at gmail.com>:

Follow-up of bpo-32086, bpo-32096 and "[Python-Dev] Python initialization and embedded Python" thread:
https://mail.python.org/pipermail/python-dev/2017-November/150605.html

I propose to explicitly list functions that can be safetely called before Py_Initialize(). This safety warranty must be part of the C API.

Maybe we should even test all tests function in test_capi using Programs/_testembed, as we did for Py_DecodeLocale() and Py_SetProgramName() in commit 9e87e7776f7ace66baaf7247233afdabd00c2b44 ("pre_initialization_api" test).

Attached PR adds proposed documentation. It also documents "global configuration variables" like Py_DebugFlag.

----------
assignee: docs at python
components: Documentation
messages: 306894
nosy: docs at python, eric.snow, ncoghlan, vstinner
priority: normal
severity: normal
status: open
title: Document functions safe to be called before Py_Initialize()
versions: Python 3.7

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue32124>
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