[9323] Fixes in code work with original caster guid.
* Add 2 function for 2 used way for original caster
- GetAffectiveCaster(), is posible NULL unit as source spell affects
(explcit caster, GO owner, caster of aura that trigering affect)..
- GetCastingObject(), possible NULL world object as in game spell effects
source, cast center, etc, need because original caster can store GO
guid that apply effect around. In other cases m_caster
* Use functions and avoid use explicitly m_originalCaster
* Use GetAffectiveCaster() for fix explicit GO cast at near unit, like now fixed campfire bonus.