- TimeoutState uses nanoseconds rather than milliseconds. While this is
slightly less efficient on Windows, it's a) not the bottleneck of Lua
execution and b) we need a monotonic counter, otherwise we could
fail to terminate computers if the time changes.
- Add an exception handler to all threads.
- Document several classes a little better - I'm not sure how useful
all of these are, but _hopefully_ it'll make the internals a little
more accessible.