Core/Visibility: Pets should be always visible for group mates.

Patch by zarocks
Closes #55

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

@@ -12506,6 +12506,12 @@ bool Unit::IsAlwaysVisibleFor(WorldObject const* seer) const
         if (seer->GetGUID() == guid)
             return true;
 
+    if (Player const* seerPlayer = seer->ToPlayer())
+        if (Unit* owner =  GetOwner())
+            if (Player* ownerPlayer = owner->ToPlayer())
+                if (ownerPlayer->IsGroupVisibleFor(seerPlayer))
+                    return true;
+
     return false;
 }