Allow item links to be deleted even when other deletes and purges are disabled.

If these links are not deleted, then they will build up in the player's inventory until they can no longer log in.
Accidental deletion of links due to bugs or other causes is potentially inconvenient but on a par with items being
accidentally moved.  When a link is deleted, the target of the link is never touched.
This is a general solution that accounts for the use of links anywhere in the user's inventory.

OpenSim/Data/MySQL/MySQLXInventoryData.cs

@@ -85,11 +85,21 @@ namespace OpenSim.Data.MySQL
             return m_Folders.Delete(field, val);
         }
 
+        public bool DeleteFolders(string[] fields, string[] vals)
+        {
+            return m_Folders.Delete(fields, vals);
+        }
+
         public bool DeleteItems(string field, string val)
         {
             return m_Items.Delete(field, val);
         }
 
+        public bool DeleteItems(string[] fields, string[] vals)
+        {
+            return m_Items.Delete(fields, vals);
+        }
+
         public bool MoveItem(string id, string newParent)
         {
             return m_Items.MoveItem(id, newParent);