Unifying customization points for member types and functions: made delegate() now also act on using_ instead of using_base.
Unifying customization points for member types and functions: made delegate() now also act on using_ instead of using_base.

For some reason, it doesn't work for delegate3() if I change the type into using_base. Therefore, let's do it the other way around.

erikvalkering/smartref,erikvalkering/smartref,erikvalkering/smartref