Add missing dynabuf_readstream member

fix #277

CHANGELOG.md

@@ -1,6 +1,7 @@
 1.0.0-b31
 
 * Tidy up build settings
+* Add missing dynabuf_readstream member
 
 WebSocket
 

include/beast/core/dynabuf_readstream.hpp

@@ -145,6 +145,13 @@ public:
         return next_layer_;
     }
 
+    /// Get a const reference to the next layer.
+    next_layer_type const&
+    next_layer() const
+    {
+        return next_layer_;
+    }
+    
     /// Get a reference to the lowest layer.
     lowest_layer_type&
     lowest_layer()