Introduce detail::enabler instead of fusion::void_.

include/boost/fusion/container/list/cons.hpp

@@ -10,6 +10,7 @@
 
 #include <boost/fusion/support/config.hpp>
 #include <boost/fusion/support/void.hpp>
+#include <boost/fusion/support/detail/enabler.hpp>
 #include <boost/fusion/container/list/cons_fwd.hpp>
 #include <boost/fusion/support/detail/access.hpp>
 #include <boost/fusion/sequence/intrinsic/begin.hpp>
@@ -82,8 +83,8 @@ namespace boost { namespace fusion
                     traits::is_sequence<Sequence>
                   , mpl::not_<is_base_of<cons, Sequence> >
                   , mpl::not_<is_convertible<Sequence, Car> > > // use copy to car instead
-              , void_
-            >::type = void_()
+              , detail::enabler_
+            >::type = detail::enabler
         )
             : car(*fusion::begin(seq))
             , cdr(fusion::next(fusion::begin(seq)), mpl::true_()) {}