Prepare release

[talex5]

This has a few important bug fixes and is needed for a new release of lwt_eio (with https://github.com/ocaml-multicore/lwt_eio/pull/19).

[avsm]

Looks like the ocaml-ci needs to be updated with the latest version of dune so it recognises 3.9: /cc @tmcgilchrist.

/src: (run (shell "opam exec -- opam-dune-lint"))
File "dune-project", line 1, characters 11-14:
1 | (lang dune 3.9)
               ^^^
Error: Version 3.9 of the dune language is not supported.
Supported versions of this extension in version 3.9 of the dune language:
- 1.0 to 1.12
- 2.0 to 2.9
- 3.0 to 3.8
opam-dune-lint: internal error, uncaught exception:
                Failure("run ['dune-lint' 'describe' 'opam-files']: exited with 1")

Otherwise looks good to go!

[talex5]

Looks like the ocaml-ci needs to be updated with the latest version of dune so it recognises 3.9:

It does, but note that the opam-dune-lint check is experimental and doesn't work with Eio anyway. e.g.

eio_main.opam: changes needed:
  "fmt" {>= "0.9.0"}                       [from lib_eio_linux, lib_eio_posix, lib_eio_windows]
  "iomux" {>= "0.3"}                       [from lib_eio_posix]
  "logs" {>= "0.7.0"}                      [from lib_eio_linux]
  "uring" {>= "0.6"}                       [from lib_eio_linux]

The directories mentioned don't (directly) belong to the eio_main package and so there's no reason for it to depend on these packages.