[chord] more merkle stuff

[Benjie Chen]

josh,

so i was not completely correct when i say it was iterating thru the
entire DB. it seems that the database_get_keys method is able to skip
to the start of the region w/ some DB3 magic (hopefully the db3 is
actually do this correctly), but could we also terminate the traversal
when we hit the end of the region?  also, wouldn't it be better to do
merkle tree maintenance in the background, rather than in the path of
a block insert? since the merkle tree is more or less a soft state.

benjie

-- 
benjie chen
benjie at lcs.mit.edu