fix for case where Sequence is const

[SVN r74589]

include/boost/fusion/adapted/std_tuple/detail/size_impl.hpp

@@ -9,6 +9,7 @@
 
 #include <tuple>
 #include <boost/mpl/int.hpp>
+#include <boost/type_traits/remove_const.hpp>
 
 namespace boost { namespace fusion
 {
@@ -23,7 +24,11 @@ namespace boost { namespace fusion
         struct size_impl<std_tuple_tag>
         {
             template <typename Sequence>
-            struct apply : mpl::int_<std::tuple_size<Sequence>::value> {};
+            struct apply :
+                mpl::int_<std::tuple_size<
+                    typename remove_const<Sequence>::type>::value
+                >
+            {};
         };
     }
 }}

include/boost/fusion/adapted/std_tuple/tag_of.hpp

@@ -33,7 +33,7 @@ namespace boost { namespace fusion
 
 namespace boost { namespace mpl
 {
-    template<typename>
+    template <typename>
     struct sequence_tag;
 
     template <typename... Elements>