[PATCH 1 of 2] Add 'shelltools': diff tool detection (try to find GNU diff)

[David Champion]

* On 05 Jul 2009, David Champion wrote: 
> # HG changeset patch
> # User David Champion <dgc at uchicago.edu>
> # Date 1246838178 18000
> # Node ID 179e4915d30813050fb425b33a4f7c591b4cea50
> # Parent  a77c3ee40e4d218d9801b123ddc392072eebedfc

Much like forgetting to attach the attachment, I forgot to 'hg add
shelltools' -- resending this one.

-- 
 -D.    dgc at uchicago.edu    NSIT    University of Chicago