'boost::locale::date_time_duration' : assignment operator could not be generated

[r.korthaus@…]

boost/locale/date_time.hpp: warning C4512: 'boost::locale::date_time_duration' : assignment operator could not be generated

This is generated with MSVC12 warning level 4. Compiling with treat warnings as error is problematic.

The fix is simple, just add a deleted assignment operator:

            /// Get ending point
            ///
            date_time const &end() const { return e_; }

#if BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1800))
            // prevent warning C4512: assignment operator could not be generated
            BOOST_DELETED_FUNCTION(date_time_duration& operator=(date_time_duration const&))
#endif
        private:
            date_time const &s_;
            date_time const &e_;