Synchronization

Table of Contents
make-mailbox -- Create an empty mailbox.
send-message! -- Send a message to a mailbox.
receive-message! -- Receive a message from a mailbox.
make-send-rights -- Extract send rights from mailbox.
make-semaphore -- Create a new semaphore object, with initial count of n.
semaphore-signal -- Increment semaphore count.
semaphore-wait -- Decrement semaphore count, blocking if negative.
thread-join -- Synchronize with a thread.