S4U new features:
- Fully reimplement auto_restart mechanism that was utterly broken
(fix #22, #131 and #281 that were all very related)
+ - Implement semaphores (fix #303 and #291)
- When creating an actor from a function and its parameters,
move-only parameters are not allowed anymore, as it would prevent
the actor to be restartable if its parameters are consumed on run.
- #288: MPI_Init(NULL, NULL)
- #289: Improve documentation of Actor::on_destruction and this_actor::on_exit()
- #290: Method to check if a mailbox has a message ready to be consumed
+ - #291: [s4u] semaphores do not seem available yet
- #294: Alltoall collective implementation of mpich
- #295: Starting a Host as OFF is not supported
- #296: DTD too permissive
