[boost] [math] Missing constexpr statement in MPFR bindings

Hi, I encountered a compiler error using gcc-5.0 with the math constants in boost 1.60.0 due to a different exception specification of math::tools::digits(): The prototype defined in math/tools/precision.hpp has a BOOST_NOEXCEPT specifier, while the implementation in math/bindings/mpfr.hpp does not have the respective specification. Adding BOOST_NOEXCEPT in math/bindings/mpfr.hpp solves the problem, i.e. compilation succeeds. I was wondering whether this is a bug or whether the error can be circumvented in another way. Regards Claas