[MERGE] Quick hack to do batching in InterDifferingSerializer. Almost halves the HPSS round-trips fetching pack-0.92-subtree to 1.9-rich-root.

[John Arbash Meinel]

John Arbash Meinel has voted comment.
Status is now: Semi-approved
Comment:
I certainly approve of this, though I'll note that Robert completely 
rewrote inter-differing-serializer for the CHK code. I don't think we 
really want to wait for that change to land, though.

For details, see: 
http://bundlebuggy.aaronbentley.com/project/bzr/request/%3C20081117065938.GA18818%40steerpike.home.puzzling.org%3E
Project: Bazaar