Allow qualified reference to constructors (at least in bang-types).  A regular variant type supports qualified constructors of the form:  M.t.X.  An extensible variant type supports qualified constructors of the form:  M.t.N.X.

git-svn-id: http://caml.inria.fr/svn/ocaml/branches/constructors_with_record3@15332 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02