Reinvent boost statistical functions

[rmartinho]

https://github.com/rmartinho/nonius/blob/devel/include/nonius/detail/stats.h++ uses boost::math::quantile, boost::math::normal, and boost::math::cdf.

These need to be replaced with non-boost equivalents to remove the boost dependency.

Pretty please, oh my gosh yes! Building on my ARM targets is like russian roulette with boost as dependency, the compiler runs out of memory pretty often when cross-compilation is not available...