Merge of sam sync code from TNG.

Merge of sam sync code from TNG.

Reverse-engineered the sam replication protocol from staring at hex dumps
for a while.  It's pretty similar to the sam sync protocol with a couple of
different delta header types.

I wasn't able to figure out the format of the privilege stuff - needs more
time and a whiteboard.  (-:

The impressive bit is that the sam sync stuff from tng basically just
worked thanks mainly to Luke Leighton's efforts in this area.