The "Smoke Tests" are tiny, standalone things that do not depend implicitly
on the Prelude, but may import Prelude modules explicitly.

They are used to work out what's gone wrong when you've been hacking on the runtime
system and now every program is segfaulting.

They should test trivial things, like simple addition and printing to the screen,
and each file should contain just a single test. All tests here should compile
and run successfully. Put tests that are expected to fail somewhere else.