Needed to have ocamlfind discover ocamlgraph with Nixpkgs.

diff -x '*~' -Naur MLstate-opalang-ee92891/configure MLstate-opalang-ee92891-new//configure
--- MLstate-opalang-ee92891/configure	2011-09-30 05:41:18.000000000 -0430
+++ MLstate-opalang-ee92891-new//configure	2011-11-24 13:47:01.332558705 -0430
@@ -567,7 +567,7 @@
 fi
 
 # - checking ocamlgraph
-if ! CONFIG_LIB_OCAMLGRAPH=$(locate-ocaml-lib "Graph" "ocamlgraph/graph")
+if ! CONFIG_LIB_OCAMLGRAPH=$(locate-ocaml-lib "Graph" "ocamlgraph" "graph")
 then lib-not-found "ocamlgraph" "libocamlgraph-ocaml-dev"
 fi