Re: [PATCH v3 0/1] MR6644: Draft: msvcrt: Initialize locale data in new threads.

[Bernhard Übelacker (＠bernhardu)]

v3:
- Changed in test error message to "expected valid locale\n".
- Removed _endthread from thread function.
- Just initialize ptr->cached_locale instead of calling _setmbcp.
- Using _beginthreadex instead of _beginthread.
- Removed `__attribute__((unused))`.