oceani: minimal error tracking.

oceani: minimal error tracking.

1/ If the parser hits an error, catch it at eof by having
    Program -> ERROR
2/ Allow the presence of and error to be recorded in the context.
3/ If an error occured, don't try to run, and do exit with an error
   status.

Now, at last, we get told where the error was.

Signed-off-by: NeilBrown <neil@brown.name>