[Beman Dawes]
As of the moment, the BOOST_MSVC_ENABLE_2014_JUN_CTP macro must be defined to eliminate a bunch of macros that should not apply to the Visual Studio 2015 Preview: BOOST_NO_CXX11_ALIGNAS [no value]
FYI, alignas has a limitation in Preview that will affect any attempt to use it in aligned_storage. Specifically, classes with alignas'ed data members can't be passed by value.
BOOST_NO_CXX11_REF_QUALIFIERS [no value]
Note that Preview's STL doesn't consistently support ref-qualifiers; I'm fixing this for RTM.
In other words, the only CXX11 macros that should be defined are: BOOST_NO_CXX11_ADDRESSOF [no value]
std::addressof() is in both 2013 and 2015 Preview. I recently found a minor issue, which I'm fixing for 2015 RTM - it didn't properly handle functions. For objects it worked fine in 2013. STL