bug#22251: ghc-memory test suite fails on i686

[Mark H Weaver]

The ghc-memory test suite has failed several times in a row on i686 with
the same errors:

  http://hydra.gnu.org/build/893578

memory
  [...]
  encoding
    Bytes
      [...]
      BASE32
        [...]
        decode-KAT
          [...]
          11:                                         FAIL
            Exception: Bytes: size must be >= 0
    [...]
    ScrubbedBytes
      [...]
      BASE32
        [...]
        decode-KAT
          [...]
          11:                                         FAIL
            Exception: ScrubbedBytes: size must be >= 0

    Mark