Function mioco::offload

pub fn offload<'b, F, R>(f: F) -> R where
    F: FnOnce() -> R + 'b,
    F: Send,
    R: Send, 

Execute a block of blocking operations outside of mioco.

Mioco requires cooperative context-switching points like mioco IO, yield_now() etc. Long running CPU-intense work, or native blocking-IO could starve other coroutines.

To prevent that this call can be used to execute a block of code without blocking cooperative coroutine scheduling. This is done by offloading the synchronous operations to a separate thread, and blocking current coroutine when operation is completed.

TODO: Right now a new thread will be spawned for every call. A thread pool pulling work given on a channel, would be more efficient and prevent spawning too many threads. PRs welcome. TODO: find some wise people to confirm if this is sound