Log Message:
p5-Math-Prime-Util: update to 0.70.

0.70 2017-12-02

    [FIXES]

    - prime_count(a,b) incorrect for a={3..7} and b < 66000000.
      First appeared in v0.65 (May 2017).
      Reported by Trizen.  Fixed.

    - Also impacted were nth_ramanujan_prime and _lower/_upper for
      small input values.

    [FUNCTIONALITY AND PERFORMANCE]

    - Some utility functions used prime counts.  Unlink for more isolation.

    - prime_count_approx uses full precision for bigint or string input.

    - LogarithmicIntegral and ExponentialIntegral will try to use
      our GMP backend if possible.

    - Work around old Math::BigInt::FastCalc (as_int() doesn't work right).

    - prime_memfree also calls GMP's memfree function.  This will clear the
      cached constants (e.g. Pi, Euler).

    - Calling srand or csrand will also result in the GMP backend CSPRNG
      functions being called.  This gives more consistent behavior.

    [OTHER]

    - Turned off threads testing unless release or extended testing is used.
      A few smokers seem to have threads lib that die before we event start.

    - Removed all Math::MPFR code and references.  The latest GMP backend
      has everything we need.

    - The MPU_NO_XS and MPU_NO_GMP environment variables are documented.