Add new traits named has_no_bounds.

It is for special usecase: some thing like a window function.
This commit relative to c9ae4fc886 .
Users who wants to access out-of-bounds of sequence, specify new
category to it.

    struct sequence {
        struct category
            : fusion::random_access_traversal_tag
            , fusion::no_bounds_tag {};
        ...
    };

All of bounds related intrinsics of the /no-bounds-sequence/ *should*
guarantee to be well-defined or SFINAE-friendly, or compile error.

include/boost/fusion/support/category_of.hpp

@@ -36,6 +36,8 @@ namespace boost { namespace fusion
 
     struct associative_tag {};
 
+    struct no_bounds_tag {};
+
     namespace extension
     {
         template<typename Tag>
@@ -107,6 +109,13 @@ namespace boost { namespace fusion
                 random_access_traversal_tag
               , typename category_of<T>::type>
         {};
+
+        template <typename T>
+        struct has_no_bounds
+            : is_base_of<
+                no_bounds_tag
+              , typename category_of<T>::type>
+        {};
     }
 }}