Fix PR#6716: Assertion failure with existentials + inline records + rows

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@15675 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
add comment for Tobject in Datarepr.free_vars

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@15676 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02