+extern jb_err client_if_modified_since(struct client_state *csp, char **header);
+extern jb_err client_accept_language (struct client_state *csp, char **header);
+extern jb_err client_if_none_match (struct client_state *csp, char **header);
+extern jb_err crunch_client_header (struct client_state *csp, char **header);
+extern jb_err filter_header (struct client_state *csp, char **header);
+extern jb_err filter_client_header (struct client_state *csp, char **header);
+extern jb_err filter_server_header (struct client_state *csp, char **header);
+extern jb_err client_x_filter (struct client_state *csp, char **header);