The supported options are `-h`, `-V`, `-t`, `-T`, and `-c`.
Additional arguments are files to be loaded.
In the process, these additional changes have been made:
* `:check` has been replaced with `:printTypes`;
disabling typechecking is no longer possible.
* Ivo programs no longer allow top-level expressions;
a `main` definition must be used instead.
* Traces and type information are now printed to `STDERR`.
* The interpreter code underwent /some/ cleanup,
but more is still needed.
