Panicking tasks should abort process if not handled

RFC for issue opened here: https://github.com/rust-lang/rust/issues/19610

Sorry for being dense. But I do finally understand. Even if the user code contained no unsafe code, it may call code that's unsafe and panic unsafe. I was only thinking about the immediate safe user code. Apologies.

I only mentioned poisoning at all because on the original issue I opened, I was told abort-on-panic was unneeded as poisoning did that in Rust. Sorry for getting into an unrelated discussion and taking so long to get your point.