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- RankN1 was a bogus test.  There error didn't have anything to do with
  rank-n types, but was just due to an ambiguous signature.

This makes the testsuite more resilient when using threads

This makes things more robust when running with threads

We need to talk about the
    powerpc-apple-darwin
platform rather than the
    powerpc_apple_darwin
platform. Spotted by Claus / Thorkil.