[issue40302] Add pycore_byteswap.h header file with _Py_bswap32() function

[STINNER Victor]

Change by STINNER Victor <vstinner at python.org>:


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title: Add _Py_bswap32() function to pyport.h -> Add pycore_byteswap.h header file with _Py_bswap32() function

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue40302>
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