[boost] [tuple] typo at docs

Hello, I think there's a typo at section "Traits classes for tuple element types" in the advanced features page of Boost.Tuple docs; where it reads: "1. access_traits<T>::type maps T to the return type of the non-const access functions ..." looks like it should be: "1. access_traits<T>::non_const_type..." I can fix this myself if given permission. Thank you, Joaquín M López Muñoz Telefónica, Investigación y Desarrollo