pub/t/x*: Rearrange the Monte-Carlo tests.

  * Insert more intermediate values, specifically at every power of 10.

  * Rather than calculating the whole thing from scratch each time,
    tests other than the first one continue from the previous
    state (which I had to calculate the hard way and enter into the
    test-vector files).  The total iteration count and final results
    still match the RFC.

  * Split the very slow high-iteration-count tests into a separate file,
    where they can be run discretionally without having to edit source
    files.  Arrange to distribute these new files.