RFR: 8294594: Fix cast-function-type warnings in signal handling code [v2]

[David Holmes]

On Mon, 10 Oct 2022 12:32:39 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> After [JDK-8294314](https://bugs.openjdk.org/browse/JDK-8294314), we would have signals_posix.cpp excluded with cast-function-type warning:
>
> Aleksey Shipilev has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:
> 
>  - Naming
>  - Redo using the proper signatures
>  - Merge branch 'master' into JDK-8294594-warning-cast-function-type-signals
>  - Fix

Fix looks good as far as it goes (can't believe I didn't see what was going on here!) - but `os::signal` is still broken as it uses `sa_handler` instead of `sa_sigaction`.

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Changes requested by dholmes (Reviewer).

PR: https://git.openjdk.org/jdk/pull/10494