fundamental problem with `\autoBeamOff`

[Werner LEMBERG]

Consider this small example.

```tex
{
  f'8 f' \autoBeamOff f' f'
  f' f' f' f'
}
```

For me it was surprising to see that `\autoBeamOff` doesn't act
immediately but rather two eighths later.  The documentation doesn't
mention this, AFAICS, and I consider this behaviour rather
counter-intuitive.

Could this be fixed?


    Werner