Fixed periodic damage for stackable auras (Deadly Poison...). Patch by Lyall. Closes issue #1368.

--HG--
branch : trunk

src/server/game/Entities/Unit/Unit.cpp

@@ -3496,7 +3496,19 @@ void Unit::_AddAura(UnitAura * aura, Unit * caster)
         if (Aura * foundAura = GetOwnedAura(aura->GetId(), aura->GetCasterGUID(), 0, aura))
         {
             if (aura->GetSpellProto()->StackAmount)
+            {                       
                 aura->ModStackAmount(foundAura->GetStackAmount());
+                                           
+                // Update periodic timers from the previous aura
+                for (uint8 i = 0; i < MAX_SPELL_EFFECTS; ++i)
+                {
+                    AuraEffect *existingEff = foundAura->GetEffect(i);
+                    AuraEffect *newEff = aura->GetEffect(i);
+                    if (!existingEff || !newEff) 
+                        continue;
+                    newEff->SetPeriodicTimer(existingEff->GetPeriodicTimer());
+                }
+            }
 
             // Use the new one to replace the old one
             // This is the only place where AURA_REMOVE_BY_STACK should be used

src/server/game/Spells/Auras/SpellAuraEffects.h

@@ -45,6 +45,9 @@ class AuraEffect
         int32 GetAmount() const { return m_amount; }
         void SetAmount(int32 amount) { m_amount = amount; m_canBeRecalculated = false;}
 
+        int32 GetPeriodicTimer() const { return m_periodicTimer; }
+        void SetPeriodicTimer(int32 periodicTimer) { m_periodicTimer = periodicTimer; }
+
         int32 CalculateAmount(Unit * caster);
         void CalculatePeriodic(Unit * caster, bool create = false);
         void CalculateSpellMod();