Revert "Remove an insterface member that was never used"

It was used. By the API, which is dynamically loaded. So it didn't complain
until it hit Bamboo

This reverts commit 33d5018e94.

OpenSim/Region/ScriptEngine/Interfaces/IScriptEngine.cs

@@ -76,6 +76,7 @@ namespace OpenSim.Region.ScriptEngine.Interfaces
 
         void SetScriptState(UUID itemID, bool state);
         bool GetScriptState(UUID itemID);
+        void SetState(UUID itemID, string newState);
         void ApiResetScript(UUID itemID);
         void ResetScript(UUID itemID);
         IConfig Config { get; }