RFR: 8329816: Add SLEEF version 3.6.1

[Magnus Ihse Bursie]

On Thu, 29 Aug 2024 23:07:16 GMT, Magnus Ihse Bursie <ihse 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 is a new attempt at solving [JDK-8329816](https://bugs.openjdk.org/browse/JDK-8329816); the original attempt is here: https://github.com/openjdk/jdk/pull/19185. This PR is based on the discussions on how to move forward that was held in that original PR.

Sorry for the force push. The libsleef source code had *tons* of trailing whitespace, and it seems jcheck got stuck on that. The bot had not finished in 12 hours or so. I initially pushed an additional commit that fixed the whitespace, but jcheck goes through the commits one at a time, so that did not help.

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PR Comment: https://git.openjdk.org/jdk/pull/20781#issuecomment-2320943487