Log Message:
Update to 0.31

Upstream changes:
0.31  2013-08-07

    - Change proof certificate documentation to reflect the new text format.

    - Some platforms were using __int128 when it wasn't supported.  Only
      x86_64 and Power64 use it now.

    - Small speedup for ranged totient internals.

    - Patch MPU::GMP 0.13 giving us not quite what we expected from a small
      certificate.  Fixed in MPU::GMP 0.14, worked around here regardless.

0.30  2013-08-06

    [API Changes]
      - Primality proofs now use the new "MPU Certificate" format, which is
        text rather than a nested Perl data structure.  This is much better
        for external interaction, especially with non-Perl tools.  It is
        not quite as convenient for all-Perl manipulation.

    [Functions Added]
      - is_frobenius_underwood_pseudoprime
      - is_almost_extra_strong_lucas_pseudoprime
      - lucas_sequence
      - pplus1_factor

    [Enhancements]
      - Documentation and PP is_prime changed to use extra strong Lucas test
        from the strong test.  This matches what the newest MPU::GMP does.
        This has no effect at all for numbers < 2^64.  No counter-example is
        known for the standard, strong, extra strong, or almost extra strong
        (increment 1 or 2) tests.  The extra strong test is faster than the
        strong test and produces fewer pseudoprimes.  It retains the residue
        class properties of the strong Lucas test (where the SPSP-2
        pseudoprimes favor residue class 1 and the Lucas pseudoprimes favor
        residue class -1), hence should retain the BPSW test strength.

      - XS code for all 4 Lucas tests.

      - Clean up is_prob_prime, also ~10% faster for n >= 885594169.

      - Small mulmod speedup for non-gcc/x86_64 platforms, and for any platform
        with gcc 4.4 or newer.

    [Bug Fixes]
      - Fixed a rare refcount / bignum / callback issue in next_prime.