Catch Panic Configuration

[Drakulix]

This PR adds runtime configuration of catching panics.

When no catching is enabled, that panic is actually still catched, because coroutine-rs does execute the init_fn in a foreign function context, causing a SIGILL if a panic would occure. Instead the panic is then passed to the mio::EventLoop, where it is propageted to get a nice backtrace.

Panic catching is configurable through the Config struct, but the actual flag is passed into each coroutine to be able to read it inside the Coroutine::spawned function.

Additionally sending the panic requires the thread_id to access the right Mio::Sender, which was added to HandlerShared.

[dpc]

I don't understand this comment. Do you mean "never panic inside init_fn"?

[Drakulix]

Yes. Isn't init_fn the actual Coroutine? Sorry if that comment is misleading.

[dpc]

Well it executes in the coroutine at the begining. But you can panic in the rest of coroutine, just not in the init_fn itself.

[dpc]

Something went wrong and the hang seems real. I'm investigating if it was your patch, or previously unknown problem.

[dpc]

Travis failed without your patch. So something else, it seems.

[Drakulix]

I have answered all your comments. Once that travis build error is sorted out, I will push the name and comment changes to trigger a new build.

[dpc]

Travis hanged, looks like the existing issue yet to be fixed, so merged. Thanks!