Don't define the MSVC clz functions unless __builtin_clzll is unavailable.
Don't define the MSVC clz functions unless __builtin_clzll is unavailable.

This is mainly just to avoid including intrin.h unnecessarily.

cppformat/cppformat,mojoBrendan/fmt,cppformat/cppformat,lightslife/cppformat,dean0x7d/cppformat,alabuzhev/fmt,cppformat/cppformat,alabuzhev/fmt,lightslife/cppformat,mojoBrendan/fmt,lightslife/cppformat,dean0x7d/cppformat,mojoBrendan/fmt,alabuzhev/fmt,dean0x7d/cppformat