mode/blocker: Superclass hostlist with remote-file to simplify code.
mode/blocker: Superclass hostlist with remote-file to simplify code.

Note that now hostlist downloads are blocking, but this can be easily changed.
Benefit of making them block is that it guarantees the user that no personal
information will be leaked to blocked host.

To make it non-blocking, we could pass `wait-p nil` to `nfiles:content`.

jmercouris/NeXT,jmercouris/NeXT