std.hash.int: better handle odd bit sizes

Uses the non rational solution of a quadratic, I made it work up to 256
bits, added Mathematica code in case anyone wants to verify the magic
constant.

integers between sizes 3...15 were affected by fatal bias, it is best to
make them pass through the generic solution.

Thanks to RetroDev256 & Andrew feedback.
ae6c24b490Francesco Alemanno committed on 11/24/2024, 11:29:20 PM· committed by Andrew Kelleyparentd09fd24
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