AMD Ryzen 5 7600X gmpbench submission (result 8010.2) -- new: 9176.2

[Torbjörn Granlund]

  The result is 14.5% increase in GMPbench value, new value is 9176.2 !

That's much better, but still not as good as it should be with some
optimisation.  Specifically, there seems to be something slightly off
with the multiply performance.

Unfortunately, I don't have Zen4 hardware, nor do I the time to optimise
GMP for Zen4 anytime soon.

-- 
Torbjörn
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