Boost.Real: Improving Complexity

Real serves to tackle the pervasive problem of inaccuracy that arises from floating point arithmetic. However, there is still much to be done to get to a peer review ready state. I propose to optimize the memory usage of Real. By changing the way real_explicit stores numbers, we can reduce memory usage of real_explicit by an order of magnitude. Utilizing std::variant, we can reduce the memory used by a real number to that of either a real_operation, real_explicit, or real_algorithm. I propose to better the way Real deals with operations, in particular, by simplifying sums of multiples of the same number. Further, I propose to implement benchmarking using Google Benchmark, to allow direct comparison between Real and other representations. After this, Boost.Real may be ready for peer review.