Core/Grid:

- Simplified CellArea calculation (Original author: SilverIce)

- Removed unused code in Cell class (Original author: SilverIce)

- Improve some Visit functions.

src/server/game/Spells/Spell.cpp

@@ -600,7 +600,6 @@ WorldObject* Spell::FindCorpseUsing()
 
     CellCoord p(Trinity::ComputeCellCoord(m_caster->GetPositionX(), m_caster->GetPositionY()));
     Cell cell(p);
-    cell.data.Part.reserved = ALL_DISTRICT;
     cell.SetNoCreate();
 
     WorldObject* result = NULL;
@@ -5831,7 +5830,6 @@ SpellCastResult Spell::CheckItems()
     {
         CellCoord p(Trinity::ComputeCellCoord(m_caster->GetPositionX(), m_caster->GetPositionY()));
         Cell cell(p);
-        cell.data.Part.reserved = ALL_DISTRICT;
 
         GameObject* ok = NULL;
         Trinity::GameObjectFocusCheck go_check(m_caster, m_spellInfo->RequiresSpellFocus);