Remove unused "primitive"

[dra27]

While testing ocaml/ocaml#10926, I discovered this unused "primitive". There's not enough git history to see what was going on, but this looked highly suspect - unix_error_of_code expects a C integer which is tricky to provide from OCaml!

It's unused, so I assume it can be safely deleted.

[edwintorok]

Thanks, that may have been a leftover from some debugging I've done while writing this. I think some of these functions return an int with a meaning of errno instead of setting errno (so the usual code that raises exceptions when errno is set cannot be used), but I've fixed that in some generic wrapper code here which takes the int returned by the function and converts it and raises properly:

ocaml-dlm/lib/dlm.ml

Lines 20 to 25 in d4d37fa

	let fail_errno ?(call="") ?(label="") errno =
	let open Errno in
	Errno_unix.to_unix_exn (Error {
	errno = of_code ~host errno;
	call; label;
	}) |> Lwt.fail

It is using the Errno_unix module to do that, so this primitive can indeed be dropped.

[edwintorok]

Not sure what is wrong with the opam cache error in the CI (HTTP 503), but this change is simple enough that I'll merge it without waiting on the CI to fix itself.