[Libguestfs] [PATCH nbdkit 0/6] Various fixed for OCaml 5

(Not for review, I've already pushed this upstream as commits 35db543e3..9d4b87e03) This series fixes nbdkit for OCaml 5 (thanks Jerry James for providing the Fedora packages necessary), and I tested it and it compiles and tests fine at least as far back as OCaml 4.05. It was quite complicated and subtle getting this right, not helped by the documentation which is unclear. Basically you have to follow the OCaml source code to work out what's really going on. Rich.