autobeaming over rests

[Werner LEMBERG]

The NR says that autobeaming doesn't work over rests.  In some
situations this means a lot of additional work.  As an example,
consider a piece that uses almost exclusively a saltarello-like
rhythm:

```
\time 6/8 d8[ r d] d[ r d]
```

I now wonder whether it makes sense to control this behaviour with a
property, and whether this behaviour (i.e., autobeaming over rests)
can be easily implemented at all...


    Werner