Vision/aggro changes.

-Increase mob vision while chasing an attacker from +3 to +5 normal
vision.
-Record the time last attacked and the object who did it and use this
when determining whether to stop chasing an attacker who is fleeing
(keep fleeing for at least 10 sec after the attack, no matter if we can
see them or not). -Increase piChaser_factor to stop multiple mobs
aggroing on one player without provocation.
-Attacking a monster will always cause it to aggro; if the event passed
to GetHatred is TS_FIGHT_ME_VICTIM, the mob will ignore the amount of
chasers its target has.