[issue35365] Use wchar_t* buffer instead of Unicode object in code page decoder

[Serhiy Storchaka]

Change by Serhiy Storchaka <storchaka+cpython at gmail.com>:


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dependencies: +Code page decoder incorrectly handles input >2GiB

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue35365>
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