MSVC: Missing symbols while linking dynamically

[jimpark]

MSVC 17.5.5 complains about two internal functions missing from the DLL.

fp operator*(fp x, fp y);
fp get_cached_power(int min_exponent, int &pow10_exponent);

They need to be declared fully inlined or decorated with FMT_API.

[vitaut]

Fixed in c99a259, thanks for reporting.