Creates a thread-pool.
Destroys a thread-pool.
Calls the delegate in parallel, with 0..count as index. Immediate waiting for completion.
Same, but does not wait for completion. You cannot have 2 concurrent parallelFor for the same thread-pool.
Wait for completion of the previous parallelFor, if any.
Rewrite of the ThreadPool using condition variables. FUTURE: this could be speed-up by using futures. Description of the task and associated condition+mutex would go in an external struct. Note: the interface of the thread-pool itself is not thread-safe, you cannot give orders from multiple threads at once.