Re: [Libguestfs] [libnbd PATCH] generator: Let nbd_aio_get_direction return unsigned

The return value is a bitmask, and is already documented as never failing, hence it makes sense to return an unsigned value to make it easier to do bitwise operations without worrying about potential undefined C semantics on a signed value. --- I'm not sure if we want this, or even if we do if my OCaml was the most concise, but it matches the sentiment of our recent effort to let the valid_flag and status parameters to callbacks be unsigned.