Buff System & Map skipping fix + properly disposing Storage + Fairness to locks

Fixed buff system behaving oddly if a buff has value zero, that would render some skills "broken".
Fixed players skipping maps when trying to access portals while under a poor Internet connection.
Fixed storage not disposing players properly in cases where the players does not meet the storage conditions.
Set some locks to use fairness strategy when dealing with atomic code, in order to make the calls to it properly synchronized.
Fixed Aran introductory questline stucking players when certain conditions were met.
Added drop data for some mob versions of Fairy, Yeti and Pepe.

src/server/maps/MapleHiredMerchant.java

@@ -36,6 +36,8 @@ import java.util.Collections;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
 import net.server.Server;
 import server.MapleInventoryManipulator;
 import server.MapleItemInformationProvider;
@@ -50,7 +52,6 @@ import tools.Pair;
  * @author Ronan (concurrency protection)
  */
 public class MapleHiredMerchant extends AbstractMapleMapObject {
-
     private int ownerId, itemId, mesos = 0;
     private int channel, world;
     private long start;
@@ -62,6 +63,7 @@ public class MapleHiredMerchant extends AbstractMapleMapObject {
     private List<SoldItem> sold = new LinkedList<>();
     private AtomicBoolean open = new AtomicBoolean();
     private MapleMap map;
+    private Lock visitorLock = new ReentrantLock(true);
 
     public MapleHiredMerchant(final MapleCharacter owner, int itemId, String desc) {
         this.setPosition(owner.getPosition());
@@ -76,8 +78,11 @@ public class MapleHiredMerchant extends AbstractMapleMapObject {
     }
 
     public void broadcastToVisitorsThreadsafe(final byte[] packet) {
-        synchronized(visitors) {
+        visitorLock.lock();
+        try {
             broadcastToVisitors(packet);
+        } finally {
+            visitorLock.unlock();
         }
     }
     
@@ -90,7 +95,8 @@ public class MapleHiredMerchant extends AbstractMapleMapObject {
     }
 
     public boolean addVisitor(MapleCharacter visitor) {
-        synchronized(visitors) {
+        visitorLock.lock();
+        try {
             int i = this.getFreeSlot();
             if (i > -1) {
                 visitors[i] = visitor;
@@ -100,25 +106,33 @@ public class MapleHiredMerchant extends AbstractMapleMapObject {
             }
             
             return false;
+        } finally {
+            visitorLock.unlock();
         }
     }
 
     public void removeVisitor(MapleCharacter visitor) {
-        synchronized(visitors) {
+        visitorLock.lock();
+        try {
             int slot = getVisitorSlot(visitor);
-            if (slot < 0){ //Not found
-                    return;
+            if (slot < 0) { //Not found
+                return;
             }
             if (visitors[slot] != null && visitors[slot].getId() == visitor.getId()) {
                 visitors[slot] = null;
                 broadcastToVisitors(MaplePacketCreator.hiredMerchantVisitorLeave(slot + 1));
             }
+        } finally {
+            visitorLock.unlock();
         }
     }
 
     public int getVisitorSlotThreadsafe(MapleCharacter visitor) {
-        synchronized(visitors) {
+        visitorLock.lock();
+        try {
             return getVisitorSlot(visitor);
+        } finally {
+            visitorLock.unlock();
         }
     }
     
@@ -132,7 +146,8 @@ public class MapleHiredMerchant extends AbstractMapleMapObject {
     }
 
     public void removeAllVisitors() {
-        synchronized(visitors) {
+        visitorLock.lock();
+        try {
             for (int i = 0; i < 3; i++) {
                 if (visitors[i] != null) {
                     visitors[i].setHiredMerchant(null);
@@ -143,6 +158,8 @@ public class MapleHiredMerchant extends AbstractMapleMapObject {
                     visitors[i] = null;
                 }
             }
+        } finally {
+            visitorLock.unlock();
         }
     }
 
@@ -314,11 +331,14 @@ public class MapleHiredMerchant extends AbstractMapleMapObject {
     }
 
     public MapleCharacter[] getVisitors() {
-        synchronized(visitors) {
+        visitorLock.lock();
+        try {
             MapleCharacter[] copy = new MapleCharacter[3];
             for(int i = 0; i < visitors.length; i++) copy[i] = visitors[i];
                     
             return copy;
+        } finally {
+            visitorLock.unlock();
         }
     }
 
@@ -362,12 +382,6 @@ public class MapleHiredMerchant extends AbstractMapleMapObject {
         }
     }
     
-    public int getFreeSlotThreadsafe() {
-        synchronized(visitors) {
-            return getFreeSlot();
-        }
-    }
-    
     private int getFreeSlot() {
         for (int i = 0; i < 3; i++) {
             if (visitors[i] == null) {