add foldr/build optimisation for take and replicate
This allows take to be deforested, and improves performance of replicate and replicateM/replicateM_. We have a separate problem that means expressions involving [n..m] aren't being completely optimised because eftIntFB isn't being inlined but otherwise the results look good. Sadly this has invalidated a number of the nofib benchmarks which were erroneously using take to duplicate work in a misguided attempt to lengthen their runtimes (ToDo).
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