* Fixed the tunnel fragmentation handler to deal with multiple fragments
in a single message properly (rather than release the buffer into the
cache after processing the first one) (duh!)
* Added the batching preprocessor which will bundle together multiple
small messages inside a single tunnel message by delaying their delivery
up to .5s, or whenever the pending data will fill a full message,
whichever comes first. This is disabled at the moment, since without the
above bugfix widely deployed, lots and lots of messages would fail.
* Within each tunnel pool, stick with a randomly selected peer for up to
.5s before randomizing and selecting again, instead of randomizing the
pool each time a tunnel is needed.
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