message: Changed constexpr to const so that clang doesnt complain
diff: namespace voxblox {
  -static constexpr FloatingPoint kUnitCubeDiagonalLength = std::sqrt(3.0);
  +static const FloatingPoint kUnitCubeDiagonalLength = std::sqrt(3.0);
  template <typename VoxelType>
  void mergeVoxelAIntoVoxelB(const VoxelType& voxel_A, VoxelType* voxel_B);
  