Pass the extension instance to SignalHook-registered signal callbacks.
Review Request #6602 — Created Nov. 17, 2014 and submitted
When using SignalHook, the callback will now be passed an extension instance as a keyword argument, making it easier to operate on the extension or access settings without having to fetch the instance. Due to the changes being made here, I've also changed sandbox behavior so that we always log the error, even if we're not sandboxing.
Unit tests pass.
Used this to get the extension instance.