[clang] [Clang] Add predefined macros for integer constants to implement section 7.18.4 of ISO/IEC 9899:1999 in `<stdint.h>` in a safe way (PR #123514)

[A. Jiang via cfe-commits]

frederick-vs-ja wrote:

> > This seems related to #85995. Do you plan to fix that issue together?
> 
> I wasn't planning on fixing Clang's `<stdint.h>`, I thought it would be better handled by the maintainers of the standard library, but I can do it if you want.
> 
> Do you want me to do it?

Oh, I didn't mean that. It might be better to do that in a separated PR.

https://github.com/llvm/llvm-project/pull/123514