Minor modifications of some ocaml packages:

adds myself as a maintainer
adds assertions to have evaluation errors rather than build errors
moves opam out of ocamlPackages, as it does not provide a library

pkgs/development/ocaml-modules/sawja/default.nix

@@ -1,4 +1,7 @@
 {stdenv, fetchurl, which, perl, ocaml, findlib, javalib }:
+
+assert stdenv.lib.versionAtLeast (stdenv.lib.getVersion ocaml) "3.12";
+
 let
   pname = "sawja";
   version = "1.5";
@@ -26,10 +29,11 @@ stdenv.mkDerivation rec {
 
   propagatedBuildInputs = [ javalib ];
 
-  meta = {
+  meta = with stdenv.lib; {
     description = "A library written in OCaml, relying on Javalib to provide a high level representation of Java bytecode programs";
     homepage = "${webpage}";
-    license = stdenv.lib.licenses.gpl3Plus;
+    license = licenses.gpl3Plus;
+    maintainers = [ maintainers.vbgl ];
     platforms = ocaml.meta.platforms;
   };
 }