autochange looks ahead by only one rest

[Dan Eble]

The Notation Reference says that \autochange "looks ahead skipping over rests 
to switch in advance” and provides an example with a single rest. When there 
are multiple rests, it doesn’t move them all, which seems like a bug based on 
the NR.

I’ve prepared a patch to change this, but I haven’t created a ticket because I 
am not certain that it is a bug.  I’ve never used autochange and have no plans 
to use it; what do others think?

https://codereview.appspot.com/247370043/
See auto-change.ly for sample input.

Regards,
— 
Dan