RFR: 7903239: ofAddress factory of function pointer type is wrong for struct returns [v4]

[Maurizio Cimadamore]

On Fri, 5 Aug 2022 04:32:04 GMT, Marko <duke at openjdk.org> wrote:

>> When generating the lambda inside the `ofAddress` factory, it is missing the `SegmentAllocator` needed when the function returns a struct. This is [implemented for regular functions](https://github.com/openjdk/jextract/blob/0582eaf1b4cdba95f0ee8c2480767433bb647d0d/src/main/java/org/openjdk/jextract/impl/HeaderFileBuilder.java#L122-L127), but not for function pointers.
>
> Marko has updated the pull request incrementally with one additional commit since the last revision:
> 
>   newline

I have not sponsored this yet as the target branch of this PR seems wrong (e.g. `master` instead of `panama` or `jdk19`).

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PR: https://git.openjdk.org/jextract/pull/58