[Issue 24509] importC cannot handle _stdcall Function Calling Convention with single heading underscore

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=24509

--- Comment #3 from Ferhat Kurtulmuş <aferust at gmail.com> ---
Final fix after the reviews by the maintainers:
https://github.com/dlang/dmd/pull/16392

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