PR#6418: fix format regression on "@{<..%d..%s..>" (Benoît Vaugon)
    
    To be able to compile this patch, you should temporarily apply the
    following patch to bootstrap the format type change:
    
    > diff -Naur old/typing/typecore.ml new/typing/typecore.ml
    > --- old/typing/typecore.ml	2014-06-06 03:37:03.240926150 +0200
    > +++ new/typing/typecore.ml	2014-06-06 03:37:24.696926699 +0200
    > @@ -2956,7 +2956,7 @@
    >          | Theta rest ->
    >            mk_constr "Theta" [ mk_fmt rest ]
    >          | Formatting (fmting, rest) ->
    > -          mk_constr "Formatting" [ mk_formatting fmting; mk_fmt rest ]
    > +          mk_constr "Formatting_lit" [ mk_formatting fmting; mk_fmt rest ]
    >          | Reader rest ->
    >            mk_constr "Reader" [ mk_fmt rest ]
    >          | Scan_char_set (width_opt, char_set, rest) ->
    
    Bootstrap process:
    
      make core
      apply the patch above
      make core
      make promote-cross
      make partialclean
      revert the patch above, apply the commit
      make partialclean
      make core
      make coreboot
    
    git-svn-id: http://caml.inria.fr/svn/ocaml/version/4.02@14975 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02