Fix panic when processing ::stop --- remember to NULL various timecb_t's that are now in flux b/c of Josh's recent merkle updates.
Fix panic when processing ::stop --- remember to NULL various timecb_t's
that are now in flux b/c of Josh's recent merkle updates.

Make fetch a little more robust to FETCHITER RPCs specifying bogus
start and end values.

weidezhang/dht,weidezhang/dht,weidezhang/dht,sit/dht,sit/dht,sit/dht,weidezhang/dht,weidezhang/dht,sit/dht,sit/dht