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We don't use these for benchmarking anymore.
Now we have the go1 dir and the benchmarks subrepo.
Some have problematic copyright notices, so move out of main repo.

Preserved in golang.org/x/exp/shootout.

Fixes #12688.
Fixes #13584.

Change-Id: Ic0b71191ca1a286d33d7813aca94bab1617a1c82
Reviewed-on: https://go-review.googlesource.com/18320

Reviewed-by: Ian Lance Taylor <iant@golang.org>