Renamed driver/target to .../targetmachine to avoid confusion with the frontend file.
Cleanup: We don't support DMC.
Cleanup: Kill backend_init/term.
Factored predefined version handling code out of main().
Also factored out argument parsing to separate function.

The code is still messy, but we have to start somewhere...
De-ancient-C-ification, spelled out EXIT_SUCCESS.
Removed a few fatal() calls in argument parsing code.

global.errors is checked immediately after return anyway.
Merge pull request #487 from klickverbot/targetmachine

driver/target -> driver/targetmachine and main() cleanup