Rust threading library

Features:

• Scoped thread pool.
• Unscoped thread pool.
• Thread pool with dynamic scheduler.
• Tasks can return output.
• Tasks can share immutable context (scoped thread pool).
• Tasks are given their dispatch index when called.
• Dispatch index is always guaranteed to match the order of calls to the dispatch function.
• Atomic cells

lib.rs:

Yet another threading library intended to simplify concurrency in BP3D.