The mvst package makes use of the GSL C library. In case of
installation from source, it is necessary to download and install GSL first.
Under a Linux platform, it is possible to install the "GNU Scientific
Library (GSL) -- development package" from the package manager,
under the name "libgsl0-dev".
The structure of the configure.ac and of the Makevar.in script, needed
to interact with the GSL library, are described in
<http://dirk.eddelbuettel.com/code/rcpp/RcppGSL-intro.pdf>
The Makevar.win script has been provided by Dr. Robin K. S. Hankin, and
is also available in the gsl package
<https://cran.r-project.org/web/packages/gsl/index.html>