fixed bug in assignment operator under VC++, which was the cause of

the access violation error in graph/test/graph.cpp. The root
  of this bug is in compressed pair, which VC++ has a hard time
  generating a correct operator= for.


[SVN r8767]

include/boost/pending/iterator_adaptors.hpp

@@ -333,6 +333,14 @@ public:
       policies().initialize(iter());
     }
 
+#ifdef BOOST_MSVC
+    // This is required to prevent a bug in how VC++ generates
+    // the assignment operator for compressed_pair.
+    iterator_adaptor& operator= (const iterator_adaptor& x) {
+        m_iter_p = x.m_iter_p;
+        return *this;
+    }
+#endif
     reference operator*() const {
         return policies().dereference(type<reference>(), iter());
     }