CPP 20 compatibility

[zlnimda]

Hello there,

I recently transitioned a code base to cpp20, and <ciso646> has been deprecated.
It is recommended to use <version> instead.

This does not cause any major problem currently on msbuild with vs2022, but might not be compatible later.

[nlohmann]

Good news: this appears to already be resolved. The current header no longer includes or references <ciso646> anywhere in the codebase, so the C++20 deprecation warning this discussion raised should no longer occur on current releases.

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This reply was drafted by Claude Code on behalf of @nlohmann, as part of a review of open discussions.