Attempt to manage handles with continuations.

The discrepancy between automatic bind/unbind and manual acquire/release has been bothering me for some time now. Continuations looked like they may come in handy here, but turns out there is a pretty big problem: `try/catch blocks that use continuations cannot have finalizers`. Currently I'm getting around this by stashing the code inside the `(() => { ... })()`, but this is just way too ugly. A pity, because otherwise it looks pretty good to me.
Is there a better way around it?