[Libguestfs] [PATCH libnbd] Add bindings for Rust language

Still not working, but I took the latest patch and: - rebased it against libnbd 1.0 - fixed it so it handles new args and cbargs The generator now runs without warnings. This patch doesn't handle optargs at all. In C these are converted to non-optional parameter. Rust doesn't (AFAIK) have optional or labelled arguments unfortunately. Rich.