A never-dropping data store
Defines the Forever
struct, which provides immutable access to data
that is Sync, Send, and is never dropped. You can think of it as an Arc
with an always positive refcount.
```rust fn main() { let a = Forever::new(7u); // 7u will never be dropped. let b = a.clone() // Same underlying data.
spawn(proc() {
println!("{}", *b); // 7
});
} ```