Move to dynamic dispatch. Add support for IoAllocation* in rs.spec.

Change-Id: I013409cbb758ce5aae78347acb39c43d07aeb9bf
diff --git a/cpp/rsCppStructs.h b/cpp/rsCppStructs.h
index fcc5fc5..7a876b3 100644
--- a/cpp/rsCppStructs.h
+++ b/cpp/rsCppStructs.h
@@ -67,8 +67,7 @@
     static dispatchTable* dispatch;
 
  private:
-    static void* librs;
-
+    static bool usingNative;
     static bool initDispatch(int targetApi);
 
     bool init(int targetApi, bool forceCpu, bool synchronous);