RFR: 8294594: Fix cast-function-type warnings in signal handling code [v3]

[Aleksey Shipilev]

On Mon, 17 Oct 2022 13:40:23 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 pull request now contains five commits:
> 
>  - Merge branch 'master' into JDK-8294594-warning-cast-function-type-signals
>  - Naming
>  - Redo using the proper signatures
>  - Merge branch 'master' into JDK-8294594-warning-cast-function-type-signals
>  - Fix

Build system changes now merged with upstream (look how nice they are). Ready to integrate.

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