Access from OCaml SVMs provided by the R e1071 and svmpath packages.

OCaml functions to drive the RBF and linear kernel SVMs of the R e1071 package
and the linear kernel SVM of the R svmpath package.

This is low level on purpose: we don't provide access to all functionalities
offered by the R packages.

This is probably not high performance: data are exchanged between
R and OCaml via ASCII files.