[MERGE] groupcompress (brisbane)

[Ian Clatworthy]

Robert Collins wrote:

> That said:
>  - the name could be changed even after landing in bzr.dev, lets not
> block on that. We could go with ljcompress or something if you wanted,
> but as groupcompress isn't part of the UI for brisbane-core I'm not sure
> it matters at all.
>  - Lets do it.

I like the sound of ljcompress. The name does end up in repo
description strings so I think we want to go with it sooner rather
than later unless someone objects (or provides a beter name).

Ian C.