failed to compile ocamlgraph

```
$NPMBIN/bsc -c `ocamldep -sort *.ml *.mli`     
File "idents_analysis.ml", line 57, characters 30-37 step3/1360 when compiling mincut.ml
File "js_implementation.ml", line 87, characters 24-31 Compilation fatal error, stacktrace saved into bsc.dump
Fatal error: exception File "idents_analysis.ml", line 59, characters 18-24: Assertion failed
```
