[libc++] Makes saturation functions privately available. (#89503)

These functions are useful in the implementation of the time zone
database. So expose them with private names.

The functions could be exposed before C++ 20, but since libc++ is mostly
C++ 17 complete it seems less useful to allow earlier.

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Co-authored-by: Hristo Hristov <zingam@outlook.com>
GitOrigin-RevId: 31e769cfadf0bd99a990508600ef5bfeaaf44b0d
1 file changed