primecount-7.9-bp156.1.5

- Update to primecount-7.9 (API & ABI are backwards compatible).
- Add unit tests for pi_gourdon(x) function.
- Fix Appveyor CI tests.
- Update to latest libprimesieve-11.1.

- Update to primecount-7.8 (API & ABI are backwards compatible).
- Fix pi(-n) issue for 128-bit integers.

- Update to primecount-7.7 (API & ABI are backwards compatible).
- Fix pi(-1) crash.
- test/api.cpp: Add pi(-1) test.
- test/api_c.c: Add primecount_pi(-1) test.
- test/nthprime.cpp: Add new test.
- primecount.h: Fix -Wstrict-prototypes warning.

- Update to primecount-7.6 (API & ABI are backwards compatible).
- Requires latest primesieve-11.0 library.
- Fix missing header include in print.hpp.

- Update to primecount-7.4 (API & ABI are backwards compatible).
- Compatible with latest primesieve-8.0 library.
- Sieve.cpp: Improved pre-sieving.
- Sieve.cpp: Optimize COUNT_UNSET_BIT() macro.
- Split up main CMakeLists.txt into multiple modules.
- Reduced the number of memory allocations.

- Update to primecount-7.3 (API & ABI are backwards compatible).
- Improved big.Little CPU detection.
- Improved nth prime performance for small n.
- Reduced the number of memory allocations.
- Many CMake build system improvements.

- Add pkg-config/pkgconf support (primecount.pc).
- Improved cache size detection on big.LITTLE CPUs.
- Improved C/C++ API documentation (libprimecount.md).

- Update to primecount-7.1 (API & ABI are backwards compatible).
- Minor pi(x) & phi(x, a) speed improvements.
- PhiTiny.cpp: Use compressed phi(x, a) lookup table.
- phi.cpp: More correct usage of recursive phi(x, a) formula.
- PiTable.cpp: Add PrimePi(x) lookup table for x < 64 * 240.
- generate_phi.hpp: More correct usage of recursive phi(x, a) formula.
- nth_prime.cpp: Cache small primes <= 1009.
- nth_prime.cpp: Improve error handling, n must be >= 1.
- appveyor.yml: Fix debug build.

- Update to primecount-7.0 (API & ABI are backwards compatible).
- AC.cpp: New algorithm with improved scaling.
- AC_libdivide.cpp: New algorithm with improved scaling.
- B.cpp: Improved scaling due to independent threads.
- P2.cpp: Improved scaling due to independent threads.
- LoadBalancerAC.cpp: New thread scheduler for AC algorithm.
- LoadBalancerS2.cpp: Improve load balancing of S2_hard & D.
- LoadBalancerP2.cpp: Rewritten, now similar to other load balancers.
- SegmentedPiTable.cpp: Decrease size to x^(1/4).
- util.cpp: Improve scaling using larger default alpha_z = 2.
- imath.hpp: Optimize ilog2() & next_power_of_2() using __builtin_clzll().

- Update to primecount-6.4.
- Fixed an integer overflow in the B formula.
- Reduced memory usage of SegmentedPiTable by 1.5x.

- Update to primecount-6.2

- Update to primecount-6.1

- address review feedback

- Add libprimecount documentation

- Initial package version