Core/Spells: Fix spelleffect sanctuary

- No longer removes every attacker, but updates the visibility
  - Using that effect won't remove attackers that can still see through the stealth of the caster based on distance
- Ignores spells that were casted before or at the same time of that effect
- Trigger other needed spells when casting Shadowmeld

--HG--
branch : trunk

src/server/game/Combat/HostileRefManager.cpp

@@ -185,3 +185,18 @@ void HostileRefManager::setOnlineOfflineState(Unit *pCreature, bool bIsOnline)
 
 //=================================================
 
+void HostileRefManager::UpdateVisibility()
+{
+    HostileReference* ref = getFirst();
+    while (ref)
+    {
+        HostileReference* nextRef = ref->next();
+        if (!ref->getSource()->getOwner()->canSeeOrDetect(getOwner()))
+        {
+            HostileReference* nextRef = ref->next();
+            ref->removeReference();
+            delete ref;
+        }
+        ref = nextRef;
+    }
+}