tiny change to header

[noudess]

mob.h - The default for item slot was 0xFFFFFFF (which I assume was an attempt at -1). The argument is unsigned, so every spell was thinking it was an item slot as the value was some huge #. I think that's not intended? This large # never matched a slot, but I don't think you wanted that? I changed rge default param to be 0 in two spots:

   virtual bool CastSpell(uint16 spell_id, uint16 target_id, uint16 slot = 10, int32 casttime = -1, int32 mana_cost = -1, uint32* oSpellWillFinish = 0, uint32 item_slot = 0x0, uint32 timer = 0xFFFFFFFF, uint32 timer_duration = 0, uint32 type = 0, int16 *resist_adjust = NULL);^M
    virtual bool DoCastSpell(uint16 spell_id, uint16 target_id, uint16 slot = 10, int32 casttime = -1, int32 mana_cost = -1, uint32* oSpellWillFinish = 0, uint32 item_slot = 0x0, uint32 timer = 0xFFFFFFFF, uint32 timer_duration = 0, uint32 type = 0, int16 resist_adjust = 0);^M