primesieve-12.4

This is a maintenance release, the C/C++ API and ABI are fully backwards compatible with primesieve-12.*

ChangeLog

• Move x86 CPUID code from cpuid.hpp to src/x86/cpuid.cpp.
• multiarch_x86_popcnt.cmake: Detect x86 POPCNT support.
• CMakeLists.txt: Use CMake list for all compile time definitions.
• CMakeLists.txt: Use CMake list for all link libraries.