dinput: Convert IDirectInput into multi-interface object.
diff --git a/dlls/dinput/dinput_private.h b/dlls/dinput/dinput_private.h
index a371263..a9d12de 100644
--- a/dlls/dinput/dinput_private.h
+++ b/dlls/dinput/dinput_private.h
@@ -30,7 +30,11 @@
 typedef struct IDirectInputImpl IDirectInputImpl;
 struct IDirectInputImpl
 {
-    const void                 *lpVtbl;
+    const IDirectInput7AVtbl   *lpVtbl;
+    const IDirectInput7WVtbl   *lpVtbl7w;
+    const IDirectInput8AVtbl   *lpVtbl8a;
+    const IDirectInput8WVtbl   *lpVtbl8w;
+
     LONG                        ref;
 
     CRITICAL_SECTION            crit;