Add typings for bool __{r,}{and,or,xor}__

[asottile]

Resolves #1793

[asottile]

I want to add a test for this, but I'm not sure where to do that -- in mypy?

[JelleZijlstra]

Typeshed itself doesn't yet support test cases for individual stubs (there's an open issue for that).

For now, you can show a test program in a comment here and the mypy output to show that it works correctly.

[asottile]

Cool, the short test program is included in the issue itself