Function current_id

include/boost/leaf/error.hpp:584–589

namespace detail
{
    inline int current_id() noexcept
    {
        unsigned id = tls::read_current_error_id();
        BOOST_LEAF_ASSERT(id == 0 || (id&3) == 1);
        return int(id);
    }

    inline int new_id() noexcept
    {