[issue21955] ceval.c: implement fast path for integers with a single digit

[Yury Selivanov]

Yury Selivanov added the comment:

> Anybody still looking at this? I can take another stab at it if it's still in scope.

There were some visible speedups from your patch -- I think we should merge this optimization.  Can you figure why unpack_sequence and other benchmarks were slower?

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nosy: +yselivanov

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<http://bugs.python.org/issue21955>
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