std::popcount not found when compiling with msvc 2019 x64

Hi,

When building with /std:c++latest on msvc 2019, compiler complain

`error C2039: 'popcount': is not a member of 'std'` in qalgorithms.h file

when adding #include <bit> on top of the header, the issue is fixed and the projet compile and run fine, so the problem is the detection of __cplusplus, it seems that msvc don't set the value of __cpluscplus (and set it to 199711) which cause the non inclusion of <bit> header