+/**
+ * check if given string is a valid command line for any receiver
+ *
+ * \param \ra string of the form receiver_name:options
+ * \param receiver_num contains the number of the receiver upon success
+ *
+ * This function checks whether \a ra starts with the name of a supported
+ * paraslash receiver, optinally followed by a colon and any options for that
+ * receiver. If a valid receiver name was found and further are present, the
+ * remaining part of \a ra is passed to that receiver's config parser.
+ *
+ * \return On success, a pointer to the gengetopt args info struct is returned
+ * and \a receiver_num contains the number of the receiver. Otherwise this function
+ * returns \p NULL.
+ */