Merge Parsetree representation of sig/str items.

git-svn-id: http://caml.inria.fr/svn/ocaml/branches/merge_sig_str@15623 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
Merge common items in the parser.

git-svn-id: http://caml.inria.fr/svn/ocaml/branches/merge_sig_str@15624 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
Merge exception/extension constructor declarations between signatures and structures.  The type-checker rejects rebinding in signatures.

git-svn-id: http://caml.inria.fr/svn/ocaml/branches/merge_sig_str@15625 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02
Allowing val declarations in structures, syntactically, and reject them in the type-checker.

git-svn-id: http://caml.inria.fr/svn/ocaml/branches/merge_sig_str@15626 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02