libc: Add <inttypes.h> C23 feature test macro

[kfv]

Summary

Define __STDC_VERSION_INTTYPES_H__ now that the header fully
conforms to C23.

[fuz]

I trust you that you have checked that it is.

It could be helpful for documentation to add the revisions where you made inttypes.h compliant into the stack using “Edit related revisions.”

Approved for commit.

[kfv]

Thanks, Robert! Sure, I will do.