Enable interruptions in JS

Enabling periodic interruptions in javascript would allow us to checkForInterrupt without an outside thread (allowing us to detect killop/ socket disconnect without things like the killop listener).

The main impediment here is that the default interruption mechanism is signal based, and that we make syscalls from javascript which we don't intend to receive eintr.  We can remove that signal handler, but need to measure the performance impact.

If we don't do something in this space, socket disconnect is killop won't work for javascript