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

Okay I agree it makes no sense to have `os::signal` as shared code because you can't use it in a platform independent manner.

I can take that new bug (thanks @kimbarrett ) unless @shipilev  really wants it? :)

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