Lwt 5.3.0

[aantron]

Changelog:

• Add let* and and* in Lwt.Syntax and Lwt_result.Syntax (Define let*, and* ocsigen/lwt#775, Rahul Kumar).
• Add Lwt_result.both (Define let*, and* ocsigen/lwt#775, Rahul Kumar).
• Always use libev if detected (Tell libev to use kqueue by default on macOS ocsigen/lwt#601).

[camelus]

Commit: 7675ab3

A pull request by opam-seasoned @aantron.

☀️ All lint checks passed 7675ab3

• These packages passed lint tests: lwt.5.3.0

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☀️ Installability check (+1)

• new installable packages (1): lwt.5.3.0

[aantron]

Closing, because ocsigen/lwt#776 will also add let+. I will retag and send 5.3.0 again. cc @craigfe