ocaml-r needs a recent version of alcotest
ocaml-r needs a recent version of alcotest

otherwise it fails with:

```
 File "tests/conversions.ml", line 60, characters 14-20:
 60 |     Alcotest.(check' (array (float 0.000001)))
                    ^^^^^^
 Error: Unbound value check'
 Hint: Did you mean check?
```

djs55/opam-repository,pirbo/opam-repository,codinuum/opam-repository,hannesm/opam-repository,nberth/opam-repository,c-cube/opam-repository,yallop/opam-repository,emillon/opam-repository,pirbo/opam-repository,djs55/opam-repository,fpottier/opam-repository,ocaml/opam-repository,seliopou/opam-repository,mjambon/opam-repository,Chris00/opam-repository,nberth/opam-repository,lefessan/opam-repository,pqwy/opam-repository,astrada/opam-repository,jonludlam/opam-repository,yallop/opam-repository,lefessan/opam-repository,abate/opam-repository,kkirstein/opam-repository,kkirstein/opam-repository,c-cube/opam-repository,toots/opam-repository,Leonidas-from-XIV/opam-repository,andersfugmann/opam-repository,ocaml/opam-repository,codinuum/opam-repository,pqwy/opam-repository,toots/opam-repository,emillon/opam-repository,jhwoodyatt/opam-repository,jonludlam/opam-repository,Chris00/opam-repository,andersfugmann/opam-repository,hannesm/opam-repository,mjambon/opam-repository,astrada/opam-repository,jhwoodyatt/opam-repository,seliopou/opam-repository,Leonidas-from-XIV/opam-repository,fpottier/opam-repository