Begin implementing SimpleMesh and fix some bugs with refcounting and java object destruction tracking.

graphics/java/android/renderscript/ProgramStore.java

@@ -81,8 +81,11 @@ public class ProgramStore extends BaseObj {
     }
 
     public void destroy() {
+        if(mDestroyed) {
+            throw new IllegalStateException("Object already destroyed.");
+        }
+        mDestroyed = true;
         mRS.nProgramFragmentStoreDestroy(mID);
-        mID = 0;
     }