testsuite for Digest.to_hex (patch by ygrek)

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@13980 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
PR#5111: additional class for info tags

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@13982 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02