#6182: better error message for virtual objects and class types.

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@14155 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
#6180: efficient creation of uninitialized float arrays.

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@14156 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02