Implement IPC/Semaphores/Monitors Using One of the Others

[iainworkman]

Either:

• IPC using Semaphores [Same, but send semaphore instead of cv in message]
• IPC using Monitors [Store condition variable in message, wait on it in send, signal it on reply]
• Semaphores using Monitors
• Semaphores using IPC
• Monitors using Semaphores [Store number waiting and semaphore of 0 per cv]
• Monitors using IPC