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)))
 

src/main/server.cl

@@ -34,6 +34,11 @@ generic function handle-server-error to handle server errors."))
 	   (setf (connection-state connection) :processing-request))
   (:documentation "Read a request from the connection."))
 
+(defgeneric get-request-class-using-server (server version)
+  (:documentation
+   "Based on the version given, return the appropriate class for the
+request."))
+
 (defgeneric serve-request (server request)
   (:documentation
    "Let the server handle the request, creating a valid response
@@ -46,6 +51,13 @@ request, using the detailed information provided by the resource, via
 CREATE-RESPONSE.  A server must implement apropriate methods for this
 generic function, to ensure conformant generation of response messages."))
 
+(defgeneric get-response-class-using-server (server request)
+  (:documentation
+   "Return the class to be used in creating the response object based
+on the server and the class of the request object passed.  This shall
+be used by `create-response-using-server' to determine the class to be
+passed to `make-instance'."))
+
 (defgeneric write-response (server connection response)
   (:method :before (server connection response)
 	   (declare (ignorable server response))
@@ -88,6 +100,9 @@ connection."))
 (defmethod read-request ((server http-server/0.9) connection)
   (parse-request server (connection-stream connection)))
 
+(defmethod get-request-class-using-server ((server http-server/0.9) version)
+  (get-request-class nil))
+
 (defmethod serve-request ((server http-server/0.9) request)
   (let ((resource (namespace-lookup-url (http-server-namespace server)
 					(request-url request))))
@@ -105,12 +120,15 @@ connection."))
 (defmethod create-response-using-server
     ((server http-server/0.9) request status-code &rest args)
   (apply #'make-instance
-	 (get-response-class (get-http-version 0 9))
+	 (get-response-class-using-server server request)
 	 :server server
 	 :request request
 	 :status-code status-code
 	 args))
 
+(defmethod get-response-class-using-server ((server http-server/0.9) request)
+  (get-response-class (get-http-version 0 9)))
+
 (defmethod handle-server-error ((server http-server/0.9) connection condition)
   (ignore-errors
     (let ((response (make-instance