Rename inttypes.hpp to int128.hpp
Include min_max.hpp
Fix 128-bit bug

std::numeric_limits<int128_t>::max() does not work, use my own
prt::numeric_limits<int128_t>::max() instead.
Refactoring
Rename make_signed_workaround to prt::make_signed
Remove std::enable_if
Fix 128-bit bug

std::numeric_limits<T>::max() does not work with int128_t