xauth: add a configuration string option to be passed to XAuth instances

The configuration string is appended to the XAuth backend name, separated by
a colon. The configuration string is passed untouched to the backend, where
it can change the behavior of the XAuth module.

src/libcharon/plugins/xauth_noauth/xauth_noauth.h

@@ -42,9 +42,11 @@ struct xauth_noauth_t {
  *
  * @param server	ID of the XAuth server
  * @param peer		ID of the XAuth client
+ * @param profile	configuration string
  * @return			xauth_noauth_t object
  */
 xauth_noauth_t *xauth_noauth_create_server(identification_t *server,
-										   identification_t *peer);
+										   identification_t *peer,
+										   char *profile);
 
 #endif /** XAUTH_NOAUTH_H_ @}*/