testsuite/external: upgrade xml-light to 2.3

git-svn-id: http://caml.inria.fr/svn/ocaml/version/4.01@14390 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
better quoting for environment variables under Windows

git-svn-id: http://caml.inria.fr/svn/ocaml/version/4.01@14402 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
PR#6165: Alterations to handling of \013 in source files breaking other tools

git-svn-id: http://caml.inria.fr/svn/ocaml/version/4.01@14404 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
fixed misplaced bug fixes

git-svn-id: http://caml.inria.fr/svn/ocaml/version/4.01@14408 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
PR#6189, item (2): missing options in the doc

git-svn-id: http://caml.inria.fr/svn/ocaml/version/4.01@14409 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
PR#6267: more information printed by "bt" command of ocamldebug

git-svn-id: http://caml.inria.fr/svn/ocaml/version/4.01@14417 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
PR#6183: enhanced documentation for 'Unix.shutdown_connection'

git-svn-id: http://caml.inria.fr/svn/ocaml/version/4.01@14418 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02