[BUG] jsoo's `Int64.of_string` fails while ocaml's does not

[bzy-debug]

Describe the bug

With the same input, jsoo's Int64.of_string fails while ocaml's succeeds.

code example:

let () =
  Printf.printf "%Ld" (Int64.of_string "0u17965325103354776697")

How to reproduce

check out https://github.com/bzy-debug/jsoo-int64-bug

Expected behavior

jsoo prints the same value as ocaml

version

ocaml 5.2.0
js_of_ocaml 5.8.2

[hhugo]

Thanks, fix in #1666