6.0.0

Additions

Lwt_direct: a package/library for using Lwt in direct-style. (Simon Cruanes, #1060)
Lwt_runtime_events: a package/library for emmitting runtime-events.

Lwt_main.enter_iter_hooks, leave_iter_hooks, and exit_hooks are removed, use Lwt_main.*_hooks instead.
Lwt_unix.run is removed, use Lwt_main.run instead.
Async method "switch" is removed, it has been a synonym for "detach" for a while, use detach instead.
Lwt_unix.execute_job is removed, use run_job instead.

Lwt_unix notifications are now given an abstract type (Lwt_unix.notification) instead of int.
Lwt requires OCaml 4.14 or higher, Lwt_direct requires OCaml 5.0, Lwt_runtime_events requires OCaml 5.1.
Lwt_ppx emits location information (to support runtime events), incompatible with previous versions of Lwt.
Exception filter defaults to letting Out_of_memory and Stack_overflow exceptions through.
In Lwt_io, functions that create sockets gain new options ?set_tcp_nodelay and ?prepare_fd. (#1061, Simon Cruanes)
?set_tcp_nodelay is set to true by default which means TCP_NODELAY is now set by default for such functions. (#1061, Simon Cruanes)