Tracking: Changes in the next version of Stan

- We should use `stan::rng_t` instead of `boost::ecuyer1988`: https://github.com/stan-dev/stan/pull/3263
- We can drop the specific dependency on `mingw32-make` on Windows: https://github.com/stan-dev/math/pull/2999
