* marked boost::flyweight ops as noexcept where applicable
* noexcept-annotated flyweight_core to see if it helps with msvc 14.2 spurious error
* reverted
* temporarily dropped one BOOST_NOEXCEPT specifier
* restored noexcept and rmoved usage of boost::addressof
* restored boost::addressof and bypassed use of get() in operator==
* consolidated previous commit as a workaround