Most of the names have been brought in line with the names used in
testing/BenchmarkResult. For example, NsOp becomes NsPerOp.
Additionally, "Bench" becomes "Benchmark" and "BenchSet" becomes "Set".
Change-Id: I7dfca68a804e285a87ab9692b5bb99ccb676da7f
Reviewed-on: https://go-review.googlesource.com/2610
Reviewed-by: Rob Pike <r@golang.org>