Get an iterator to one past the end element in a buffer sequence.

template<
    typename C>
auto buffer_sequence_end(
    const C & c,
    constraint_t< !is_convertible< const C *, const mutable_buffer * >::value >  = 0,
    constraint_t< !is_convertible< const C *, const const_buffer * >::value >  = 0,
    constraint_t< !is_convertible< C, mutable_buffer >::value >  = 0,
    constraint_t< !is_convertible< C, const_buffer >::value >  = 0);