Jeck - Quad locking restored, minor cache fiddling.

* Restored quad locking to textures, but ignore quad locks when Release(JTexture*) is explicitly called. (I just copied and modified the code from the template, rather than do anything elegant). 
* Some minor fiddling with cache error states.

projects/mtg/include/WCachedResource.h

@@ -66,6 +66,7 @@ public:
   void Refresh();
   unsigned long size();  
   bool isGood();
+  bool isLocked();    //Is the resource locked?
   bool Attempt(string filename, int submode, int & error);
   bool compare(JTexture * t) {return (t == texture);};
   JTexture * Actual(); //Return this texture as is. Does not make a new one.