Misc fixes / Perl exports

Fix for special attack NPC_CHASE_DISTANCE to now work correctly
Perl export: NPC GetAttackDelay
Perl export: NPC GetAvoidanceRating
Perl export: NPC AddMeleeProc
Special Attacks will no longer be able to hit immune to melee / bane only flagged NPCs.
Fix for a few problems with Perl GetSpellStat