Panic resource cleanup

[roblabla]

So right now I'm not cleaning up any resource on panic (since we're simply aborting). This is obviously not good. My plan thus far was to rely on the unwinder (#13) to do the job, but maybe that's not such a good idea, as various things still cause aborts:

• panics during unwinding
• OOM, and in general most panics in memory management.

[FenrirWolf]

Unwinding is still a good idea even if it doesn't solve those specific problems, since ideally those situations would be a lot more rare than a typical panic. I'm not sure how you'd go about gracefully recovering from a situation that calls for a true abort though.