RFR: 8329816: Add SLEEF version 3.6.1

[Mikael Vidstedt]

On Fri, 10 May 2024 22:32:29 GMT, Mikael Vidstedt <mikael at openjdk.org> wrote:

> [JDK-8312425](https://bugs.openjdk.org/browse/JDK-8312425) is looking to optimize vector math operations by leveraging the SLEEF library. For legal reasons the actual contribution of the SLEEF files needs to be handled separately. This enhancement adds the relevant files, enabling the rest of [JDK-8312425](https://bugs.openjdk.org/browse/JDK-8312425) to move forward.

I, too, envision that we'll be importing header files (only). That said, I'd very much prefer *not* to rename them as part of the import. If anything I could see us have architecture specific directories in which we place the respective files (and a common directory for `misc.h`), but it's not immediately clear to me that it's worth it given that the files are used in such a narrow context in the JDK.

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PR Comment: https://git.openjdk.org/jdk/pull/19185#issuecomment-2128767164