[boost] [core] Move underlying_type to type_traits?

Subject: [boost] [core] Move underlying_type to type_traits?
From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2014-06-04 16:28:37

While documenting and cleaning up scoped_enum.hpp I factored out the 
underlying_type trait to a separate header. Mostly, because I didn't want to 
#include <type_traits> in scoped_enum.hpp. boost::underlying_type should be 
equivalent to std::underlying_type, except that it also supports emulated 
scoped enums.

Perhaps boost/core/underlying_type.hpp should be moved to Boost.TypeTraits?