PR#5891: support rectypes tag for mlpack (ocamlbuild)

git-svn-id: http://caml.inria.fr/svn/ocaml/version/4.00@13244 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
PR#5880: 'Genlex.make_lexer' documention mentions the wrong exception

git-svn-id: http://caml.inria.fr/svn/ocaml/version/4.00@13246 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
PR#5840: improved documentation for 'Unix.lseek'

git-svn-id: http://caml.inria.fr/svn/ocaml/version/4.00@13247 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02