Update tzcode to 2023c.

[des]

Summary

MFC after: 3 weeks
Sponsored by: Klara, Inc.

[des]

Add offtime_r to symbol map.

[des]

Note that this update adds a non-standard offtime_r() which is to offtime() what gmtime_r() is to gmtime(). I have submitted a similar patch (minus the pthread stuff) upstream. We do not provide public prototypes or documentation for offtime() or offtime_r(), but that's easy to fix should we decide to do so.

[philip]

Thanks for doing this! My builds are still running. I'll take a closer look at this patch my morning.

Adding offtime_r() is sensible. Thanks for submitting it upstream too. Fewer local patches is better.

[philip]

This branch passes my build tests and my functional tests.
Please let it sit in main for a couple of days before merging to stable.

Thanks for doing this!