Hi Guix!

this small patch series update ocaml to 4.11.1. The first patch adds
ocaml 4.11.1, the second adds findlib for 4.09, the third add
package-with-ocaml4.09 (along with ocaml4.09-dune, which I can't put in
a separate patch without breaking something). Then, three patches fix
the build of three packages (with these patches, they build fine with
4.09 and 4.11).  The last patch performs the final switch to 4.11.
Easier than I expected! :)

Note that with that, previously unreproducible packages are
reproducible!