liblwt-ocaml-dev 2.4.3-4 (armhf binary) in ubuntu trusty

 Lwt is a library of cooperative threads implemented in monadic style.
 With respect to preemptive threads, cooperative threads are not using
 a scheduler to distribute processor time between threads. Instead of
 this, each thread must tell the others that he wants to let them
 work.
 .
 This package contains all the development stuff you need to use the
 core Lwt OCaml library in your programs.