[MERGE] Don't buffer inventory lines during autopack

[Ian Clatworthy]

John Arbash Meinel wrote:

> This patch just changes it so that if we won't use the inventory lines,
> we just don't generate them. It should reduce CPU consumption because we
> aren't extracting the lines, and reduce memory consumption dramatically
> on large repositories. (On the OOo conversion, I quickly reached >1GB of
> memory, while with this patch autopack stayed <300MB.)

bb:approve

Thanks heaps for this.

Ian C.