RFR: 8344646: The libjsig deprecation warning should go to stderr not stdout

[Chris Plummer]

On Wed, 20 Nov 2024 21:18:01 GMT, David Holmes <dholmes at openjdk.org> wrote:

> In JDK 16 we deprecated the old signal and sigset signal-chaining interfaces under [JDK-8257572](https://bugs.openjdk.org/browse/JDK-8257572). The deprecation warning was written to stdout but all other warnings go to stderr. Having the warning be on stdout causes interference with application output so we change it to stderr.
> 
> Testing
>  - examined signal test output (see JBS issue)
>  - tiers 1-3 sanity
> 
> Thanks

Marked as reviewed by cjplummer (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/22283#pullrequestreview-2450107678