Bug 2040609

* Description of problem:
The 



* Version-Release number of selected component (if applicable):
libnbd-1.10.2-1.el9

* How reproducible:
Dependent on the guest disk image being copied with virt-v2v, if there is a segment >= 2GiB in size with identical block allocation status, NBD.block_status will return an entry with negative "length" in the entries array.

* Steps to Reproduce:
Refer to <https://bugzilla.redhat.com/show_bug.cgi?id=2027598#c61> and onwards.

* Actual results:
Refer to <https://bugzilla.redhat.com/show_bug.cgi?id=2027598#c40> and onwards -- the "Utils.get_disk_allocated" function in virt-v2v, which is supposed to make progress in every interation of its loop, will go backwards on occasion, and decay into an infinite loop.

* Expected results:
The OCaml bindings should faithfully represent uint32_t values >= 0x8000_0000. More closely, "Utils.get_disk_allocated" in virt-v2v should always terminate.

* Additional info:
(1) This is arguably a (mild) security bug, but our analysis in <https://bugzilla.redhat.com/show_bug.cgi?id=2027598#c61> is already public.

(2) The same issue exists for C's uint64_t <-> OCaml's int64 -- this is in fact a bug (or limitation) in OCaml's type system. We can't do anything about that, at the moment, as there is no OCaml type we could widen uint64_t to. (At least we can widen C's uint32_t to OCaml's int64.)