[stree] Committed: initial stree infrastructure, and stree version of enumerators

[Paolo Carlini]

Ranjit Mathew wrote:

>Matt Austern wrote:
>  
>
>>Here's the first draft!  Sorry it took a little longer than I'd 
>>expected.
>>    
>>
>It would have been much better if you'd used
>a plain text file - among other things, it makes
>it easier to quote from it while replying.
>  
>
ps2ascii, part of the GNU Ghostscript package, works well.

Paolo.