Fix clang-cl compilation error
Fix clang-cl compilation error

In file included from benchmark.cpp:14:
.\libpopcnt.h(347,27):  error: unknown type name '__m256i'
static inline void CSA256(__m256i* h, __m256i* l, __m256i a, __m256i b, __m256i c)
KOConchobhair/libpopcnt,kimwalisch/libpopcnt,kimwalisch/libpopcnt,KOConchobhair/libpopcnt