[New Port] math/R-cran-ADGofTest: Anderson-Darling GoF test

Anderson-Darling GoF test in R with p-value calculation based on Marsaglia's
2004 paper "Evaluating the Anderson-Darling Distribution."

WWW: https://cran.r-project.org/web/packages/ADGofTest/

Reviewed by: imp (mentor), mat (mentor)
Approved by: imp (mentor), mat (mentor)
Differential Revision: https://reviews.freebsd.org/D22673