Make some distributions from the 'C++' library 'Boost'
available in 'R'. In addition, the normal-inverse Gaussian distribution
and the generalized inverse Gaussian distribution are provided. The
distributions are represented by 'R6' classes. The method to sample from
the generalized inverse Gaussian distribution is the one given in
"Random variate generation for the generalized inverse Gaussian
distribution" Luc Devroye (2012)