Work around MSVC 6, 7 bug

[SVN r35099]

include/boost/graph/adjacency_matrix.hpp

@@ -474,11 +474,13 @@ namespace boost {
     typedef adjacency_matrix_traits<Directed> Traits;
     
   public:
+#if !defined(BOOST_MSVC) || BOOST_MSVC > 1300
     // The bidirectionalS tag is not allowed with the adjacency_matrix
     // graph type. Instead, use directedS, which also provides the
     // functionality required for a Bidirectional Graph (in_edges,
     // in_degree, etc.).
     BOOST_STATIC_ASSERT(!(is_same<Directed, bidirectionalS>::value));
+#endif
 
 #ifndef BOOST_GRAPH_NO_BUNDLED_PROPERTIES
     typedef typename detail::retag_property_list<vertex_bundle_t, VertexProperty>::type