On win32 fs::rename should overwrite file if exists

[Yucong Sun]

Currently , fs::rename() will return with error 183, if destination file already exists. The standard indicate that it must overwrite file , here is the patch to use MoveFileExW instead.

GHC_INLINE void rename(const path& from, const path& to, std::error_code& ec) noexcept
{
    ec.clear();
#ifdef GHC_OS_WINDOWS
    if (from != to) {
        if (!MoveFileExW(detail::fromUtf8<std::wstring>(from.u8string()).c_str(), detail::fromUtf8<std::wstring>(to.u8string()).c_str(), (DWORD) MOVEFILE_REPLACE_EXISTING)) {
            ec = detail::make_system_error();
        }
    }
#else
    if (from != to) {
        if (::rename(from.c_str(), to.c_str()) != 0) {
            ec = detail::make_system_error();
        }
    }
#endif
}

[Steffen Schümann]

Indeed, thanks! Will push a fix with additional tests on master after my working hours.

[Steffen Schümann]

Fix released with v1.2.10