[set] Okay, giving up on constexpr till C++14 ../src/hb-set.hh:213:89: error: call to non-'constexpr' function 'const elt_t& hb_vector_size_t<elt_t, byte_size>::operator[](unsigned int) const [with elt_t = long long unsigned int; unsigned int byte_size = 64]'