MSVC 2019 warnings "conversion from 'unsigned __int64' to 'size_t', possible loss of data"

[moiwi]

Commit 41d97e1 causes several MSVC 2019 warnings with "to_unsigned(size)":
format.h(1845,57): warning C4244: 'argument': conversion from 'unsigned __int64' to 'size_t', possible loss of data (compiling source file format.cc)
format.h(1846,56): warning C4244: 'argument': conversion from 'unsigned __int64' to 'size_t', possible loss of data (compiling source file format.cc)
format.h(1863,32): warning C4244: 'argument': conversion from 'unsigned __int64' to 'size_t', possible loss of data (compiling source file format.cc)
format.h(1876,32): warning C4244: 'argument': conversion from 'unsigned __int64' to 'size_t', possible loss of data (compiling source file format.cc)
format.h(1891,30): warning C4244: 'argument': conversion from 'unsigned __int64' to 'size_t', possible loss of data (compiling source file format.cc)

[Kaaserne]

Same here:

format.h(1845): warning C4244: 'argument': conversion from 'unsigned __int64' to 'size_t', possible loss of data [D:\a\cpp-lazy\cpp-lazy\build\install\_deps\fmt-build\fmt.vcxproj]

[vitaut]

Should be fixed in f468b20.