Lwt 4.2.0: promises and concurrent I/O, also Lwt_ppx 1.2.2 and Lwt_react 1.1.2

[aantron]

From the changelog:

Additions

• Lwt.both (Add support for ppx_let ocsigen/lwt#668, Brendan Long, Jeremy Yallop).
• ppx_let support with open Lwt.Infix (Include Let_syntax module for ppx_let ocsigen/lwt#667, Brendan Long).
• Lwt_stream.of_seq (Add Lwt_stream.of_seq ocsigen/lwt#646, Hezekiah Carty).
• Lwt_io.is_closed (Expose Lwt_io.is_closed ocsigen/lwt#635, Andreas Garnaes).
• Lwt_unix.IO_vectors.byte_count (Lwt_unix.IO_vectors.length ocsigen/lwt#645, Raphaël Proust).
• Support for higher baud rates in Lwt_unix.tcgetattr and Lwt_unix.tcsetattr (unix_termios_conversion.c: Support for higher baud rates. ocsigen/lwt#678, Frédéric Fortier).
• Replacement functions in Lwt_main for deprecated functions based on Lwt_sequence (Abstract Lwt_sequence from Lwt_main hooks APIs ocsigen/lwt#660).

Bugs fixed

• 4.08 compatibility (4.08 compilation errors ocsigen/lwt#658).
• Stack overflow in Lwt_stream.iter_p (Repititve bind to the same thread might cause memory leak or stack overflow. ocsigen/lwt#432, Varun Kohli).
• Incorrect bounds check in Lwt_bytes.mincore (fix condition in mincore ocsigen/lwt#627, Cédric Le Moigne).
• Lwt_bytes.mincore will not be available in future releases of OpenBSD (OpenBSD -current has removed mincore syscall -- lwt no longer builds ocsigen/lwt#663, Kenneth Westerback).
• Missing header in the Android build (Lwt_unix: missing header on Android ocsigen/lwt#652, Justus Matthiesen).
• Build broken on MSVC (ocsigen/lwt@98303de, ocsigen/lwt@85535f7, Dmitry Bely).
• Build broken on OpenBSD (respect MAKE, properly test for mincore, fdatasync is in <unistd.h> ocsigen/lwt#672, Christopher Zimmermann).
• Lwt_io.of_bytes produces a channel with inaccurate positions (Lwt_io.of_bytes + position don't work ocsigen/lwt#636, Nathan Rebours).
• Lwt_io._.read_int behaves incorrectly on 32-bit systems (read_int incorrectly reads (-1)  ocsigen/lwt#671, reported Dmitry Bely).
• Inaccurate locations for errors related to ;%lwt (Ppx: fix loc info of sequence exp ocsigen/lwt#602, @kandu).
• (_ : t) not recognized as a catch-all pattern by the PPX (ppx: recognize constrained catch-all cases  ocsigen/lwt#640, Florian Angeletti).
• Race condition in Lwt_react.E.limit (fixed race condition in Lwt_react.E.limit ocsigen/lwt#606, Avni Fatehpuria).
• Premature deallocation in Lwt_react.E.with_finaliser and Lwt_react.S.with_finaliser (Bug in Lwt_react.with_finaliser under Flambda ocsigen/lwt#626, El-Hassan Wanas).

Miscellaneous

• New tests for Lwt_bytes, portions of Lwt_unix (Test unix bytes ocsigen/lwt#619, Test lwt bytes second part ocsigen/lwt#621, Test lwt bytes third part ocsigen/lwt#628, Test lwt unix sleeping and timeout functions ocsigen/lwt#630, Add tests for user id and group id ocsigen/lwt#673, Cédric Le Moigne, Anurag Soni).
• Test suite improvements (check for duplicate test names per suite ocsigen/lwt#656, Dave Parfitt).
• Clarifications for documentation of Lwt.try_bind, Lwt.pick (Clarify try_bind documentation ocsigen/lwt#648, Clarify the Lwt.pick ocsigen/lwt#650, Bikal Lem).
• Fixed documentation of Lwt_io.read_line (Lwt_io.read_line docs: fix EOL/EOF mix-up ocsigen/lwt#657, Yoni Levy).
• Fixed some typos (Fix some typos in code comments. ocsigen/lwt#611, Fix Lwt_react documentation. ocsigen/lwt#613, Rich Neswold).

Resolves ocsigen/lwt#675.

[camelus]

☀️ All lint checks passed b863d21

• These packages passed lint tests: lwt.4.2.0, lwt_ppx.1.2.2, lwt_react.1.1.2

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☀️ Installability check (10867 → 10870)

• new installable packages (3): lwt.4.2.0 lwt_ppx.1.2.2 lwt_react.1.1.2

[mseri]

Looks good, some packages in the revdeps are just broken, while other need upper bounds. Unless you plan to do something about them, I think we can merge and clean that up separately.

[aantron]

Yes, this looks good to merge. Thank you.