[libc] [llvm] [libc][NFC] Use user defined literals to build 128 and 256 bit constants. (PR #81746)

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lntue wrote:

> > I'm sorry for asking a bit late, but is it easy to add `'` to divide 128-bit and 256-bit numbers into 32-bit or 64-bit chunks?
> 
> Sure no worries, which one do you want 64 or 32? Shall I also fix the sage scripts?

I prefer 32-bit chunks if it does not push the constants to the next line.  Otherwise, 64-bit chunks works fine too.
It would be great for the sage scripts to be updated.  Thanks!

https://github.com/llvm/llvm-project/pull/81746