Log Message:
Update to 0.60

Upstream changes:
0.60 2016-10-09

    [ADDED]

    - vecfirstidx { expr } @n             returns first index with expr true

    [FUNCTIONALITY AND PERFORMANCE]

    - Expanded and modified prime count sparse tables. Prime counts from 30k
      to 90M are 1.2x to 2.5x faster.  It has no appreciable effect on the
      speed of prime counts larger than this size.

    - fromdigits works with bigint first arg, no need to stringify.
      Slightly faster for bigints, but slower than desired.

    - Various speedups and changes for fromdigits, todigits, todigitstring.

    - vecprod in PP for negative high-bit would return double not bigint.

    - Lah numbers added as Stirling numbers of the third kind.  They've been
      in the GMP code for almost 2 years now.  Also for big results, directly
      call the GMP code and objectify the result.

    - Small performance change to AKS (r,s) selection tuning.

    - On x86_64, use Montgomery math for Pollard/Brent Rho.  This speeds up
      factoring significantly for large native inputs (e.g. 10-20 digits).

    - Use new GMP zeta and riemannr functions if possible, making some of
      our operations much faster without Math::MPFR.

    - print_primes with large args will try GMP sieve for big speedup.  E.g.
        use bigint;  print_primes(2e19,2e19+1e7);
      goes from 37 minutes to 7 seconds.  This also removes a mistaken blank
      line at the end for certain ranges.

    - PP primes tries to use GMP.  Only for calls from other PP code.

    - Slightly more accuracy in native ExponentialIntegral.

    - Slightly more accuracy in twin_prime_count_approx.

    - nth_twin_prime_approx was incorrect over 1e10 and over 2e16 would
      infinite loop due to Perl double conversion.

    - nth_twin_prime_approx a little faster and more accurate.