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/IXInventoryData.cs

@@ -74,9 +74,38 @@ namespace OpenSim.Data
         bool StoreFolder(XInventoryFolder folder);
         bool StoreItem(XInventoryItem item);
 
+        /// <summary>
+        /// Delete folders where field == val
+        /// </summary>
+        /// <param name="field"></param>
+        /// <param name="val"></param>
+        /// <returns>true if the delete was successful, false if it was not</returns>
         bool DeleteFolders(string field, string val);
+
+        /// <summary>
+        /// Delete folders where field1 == val1, field2 == val2...
+        /// </summary>
+        /// <param name="fields"></param>
+        /// <param name="vals"></param>
+        /// <returns>true if the delete was successful, false if it was not</returns>
+        bool DeleteFolders(string[] fields, string[] vals);
+
+        /// <summary>
+        /// Delete items where field == val
+        /// </summary>
+        /// <param name="field"></param>
+        /// <param name="val"></param>
+        /// <returns>true if the delete was successful, false if it was not</returns>
         bool DeleteItems(string field, string val);
 
+        /// <summary>
+        /// Delete items where field1 == val1, field2 == val2...
+        /// </summary>
+        /// <param name="fields"></param>
+        /// <param name="vals"></param>
+        /// <returns>true if the delete was successful, false if it was not</returns>
+        bool DeleteItems(string[] fields, string[] vals);
+
         bool MoveItem(string id, string newParent);
         XInventoryItem[] GetActiveGestures(UUID principalID);
         int GetAssetPermissions(UUID principalID, UUID assetID);