Keep attributes on value declarations in .cmi files (but clear all the location fields, except if -keep-locs is used, of course).  Use this to report a warning when a value marked as [@@deprecated] is referenced (#5854)

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@14188 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02