Docs. Why not?

Also a stub for gss.Context.
Add some more type annotations

This seems to silence some warnings, though I don't know if it actually
makes the code safe in ADVANCED_OPTIMIZATIONS mode. I hope it does?
/Actually/ get null starttime and friends right

The key might be missing, in which case we get undefined. Using ==
instead of === lets it work since undefined == null, but undefined !==
null.