Modified the selection of request and response classes to take into

account the server we are servicing, so that each server only sees
and creates request/response classes he knows he can handle.  This
also makes it possible to add request/response classes in a running
system, and to run servers of different versions side-by-side in an
image without affecting each other...

src/main/messages.cl

@@ -75,10 +75,11 @@ request object, which references the given server."))
 (defmethod parse-request (server stream)
   (multiple-value-bind (method url version)
       (parse-request-line stream)
-    (let ((request (make-instance (get-request-class version)
-				  :server server
-				  :method method
-				  :url url)))
+    (let ((request (make-instance
+		    (get-request-class-using-server server version)
+		    :server server
+		    :method method
+		    :url url)))
       (parse-request-remainder request stream)
       request)))