So *resource, ~resource, [resource] are all pinned. This is counter to the
design of the kind system, but this way is a much clearer path to type safety.
Once we've established a good baseline with lots of tests, then we can try to
make raising pinned kinds work.
Resources are now defined like...
resource fd(int n) { close(n); }
Calling fd with an int will then produce a non-copyable value
that, when dropped, will call close on the given int.
