The first two fixes were caught by infer. The Big Bug(tm) remains
unfixed.
* Fixed the Leech nano power
* Fixed an unlikely nullptr dereference in ItemManager
* /toggleai now makes mobs retreat immediately, instead of waiting for
their next movement tick
* Static path mobs will now stop in place instead of retreating to
their spawn points when AI is disabled
* Changed the misleading config option name from "chunksize" to
"viewdistance", since it's actually only a third of the chunk size
This replaces the unnecessary deallocations on program termination.
Passing in the suppression list environment variable via setenv()
doesn't seem to work, so I've added a comment in the Makefile to explain
invocation.
