accomodate API change in boost.range

include/boost/xpressive/sub_match.hpp

@@ -23,6 +23,8 @@
 #include <boost/mpl/assert.hpp>
 #include <boost/type_traits/is_same.hpp>
 #include <boost/iterator/iterator_traits.hpp>
+#include <boost/range/const_iterator.hpp>
+#include <boost/range/mutable_iterator.hpp>
 #include <boost/xpressive/detail/detail_fwd.hpp>
 
 //{{AFX_DOC_COMMENT
@@ -438,11 +440,6 @@ operator + (typename sub_match<BidiIter>::string_type const &lhs, sub_match<Bidi
 // Hook the Boost.Range customization points to make sub_match a valid range.
 namespace boost
 {
-    /// INTERNAL ONLY
-    ///
-    template<typename Range>
-    struct range_mutable_iterator;
-
     /// INTERNAL ONLY
     ///
     template<typename BidiIter>
@@ -451,11 +448,6 @@ namespace boost
         typedef BidiIter type;
     };
 
-    /// INTERNAL ONLY
-    ///
-    template<typename Range>
-    struct range_const_iterator;
-
     /// INTERNAL ONLY
     ///
     template<typename BidiIter>