Revert Stephen Kelly's changes.

They should really wait until MPL's dependencies have dealt with his
changes.

include/boost/mpl/void.hpp

@@ -36,24 +36,36 @@ template< typename T >
 struct is_void_
     : false_
 {
+#if BOOST_WORKAROUND(BOOST_MSVC, < 1300)
+    using false_::value;
+#endif
 };
 
 template<>
 struct is_void_<void_>
     : true_
 {
+#if BOOST_WORKAROUND(BOOST_MSVC, < 1300)
+    using true_::value;
+#endif
 };
 
 template< typename T >
 struct is_not_void_
     : true_
 {
+#if BOOST_WORKAROUND(BOOST_MSVC, < 1300)
+    using true_::value;
+#endif
 };
 
 template<>
 struct is_not_void_<void_>
     : false_
 {
+#if BOOST_WORKAROUND(BOOST_MSVC, < 1300)
+    using false_::value;
+#endif
 };
 
 BOOST_MPL_AUX_NA_SPEC(1, is_void_)