chmod patch

[Martin Pool]

That looks good. 

A couple of points:

 - You should put your own name in the copyright in the new files, and
   add the GPL boilerplate from one of the existing files.

 - You need to check whether the behavior with downlevel clients and
   servers will be acceptable.  

 - Ideally there would be a unit test just for the chmod parser.

 - Please document the fields in chmod_struct.

 - I'm not sure we need a linked list for chmod_struct, but I haven't
   completely thought it through.

I think we can merge something like this in 2.6.

Thanks, Scott!

-- 
Martin