[Libguestfs] [PATCH 0/6] Implement OClosure.

Patches 1-4 are basically uncontroversial, straightforward refactoring and IMHO we should just push them. Possibly 1-3 should be squashed together, but I posted them separately so they are easier to review. Patches 5 and 6 together implement OClosure. Patch 5 adds the feature and is simple to understand. Patch 6 changes the Closure completion callbacks into OClosure, but because it doesn't change the position within the list of arguments the C API doesn't change at all. The Python API also doesn't change for the same reason. (The OCaml API _does_ change but not significantly). I've run out of time on this patch today because I've got meetings for the rest of the day (and it's only 11am!) However if I did have more time there would be a 7th patch in the series which renames all aio_*_callback functions to simply aio_*. eg. nbd_aio_pread_callback is renamed to nbd_aio_pread (and old nbd_aio_pread is removed). That is obviously a somewhat large albeit it mechanical API change. Rich.