module Binary:sig..end
type 
The type of binary semaphores.
val make : bool -> tmake b returns a new binary semaphore.
    If b is true, the initial value of the semaphore is 1, meaning
    "available".  If b is false, the initial value of the
    semaphore is 0, meaning "unavailable".
val release : t -> unitrelease s sets the value of semaphore s to 1, putting it in the
    "available" state.  If other threads are waiting on s, one of them is
    restarted.
val acquire : t -> unitacquire s blocks the calling thread until the semaphore s
    has value 1 (is available), then atomically sets it to 0
    and returns.
val try_acquire : t -> booltry_acquire s immediately returns false if the semaphore s
    has value 0.  If s has value 1, its value is atomically set to 0
    and try_acquire s returns true.