Dear caml develpers,

   I am working on an experimental branch to pass more information from
typedtree to lambda to enable ocaml generate user readable javascript code(
https://github.com/bobzhang/ocaml/tree/master) (online-demo:
http://zhanghongbo.me/js-demo/)

   Here I get a segfault, after I change const_block:
   Below is my minimal change:

```
type pointer_info =
  | NullConstructor of string
  | NullVariant of string
  | NAPointer

type tag_info =
  | Constructor of string
  | Tuple
  | Variant of string
  | Record
  | NA

type structured_constant =
    Const_base of constant
  | Const_pointer of int * pointer_info
  | Const_block of int * tag_info * structured_constant list
  | Const_float_array of string list
  | Const_immstring of string
```
Note that the enriched info is not used in ``emitcode``, now I get a
segfault in make world:

```
../../boot/ocamlrun ../../ocamlc -nostdlib -I ../../stdlib -c -w +33..39
-warn-error A -bin-annot -g -safe-string -I ../../stdlib -I ../../utils -I
../../typing -I ../../bytecomp -I ../../asmcomp extract_crc.ml
../../boot/ocamlrun ../../ocamlc -nostdlib -I ../../stdlib -o extract_crc
dynlink.cma extract_crc.cmo
make[3]: *** [extract_crc] Segmentation fault: 11
make[3]: *** Deleting file `extract_crc'
make[2]: *** [otherlibraries] Error 2
make[1]: *** [all] Error 2
```

Any help is appreciated : )

-- 
Regards
-- Hongbo Zhang