[boost] [fusion] Compilation errors on Intel compiler (C++14)

Hi, I'm seeing compilation errors coming from Boost.Fusion headers on Sandia-intel-17.0-c++14: http://www.boost.org/development/tests/develop/developer/output/Sandia-intel... Notably, the same tests compile fine in C++11 mode on the same compiler, which makes me think that is related to C++14 mode specifically. Looking at the code, it seems the compiler makes constexpr functions implicitly const-qualified even though it shouldn't in C++14 mode, so it's likely a compiler bug. Still, is it possible to add a workaround?