Multiple reports from one BUFR message

Starting with the next version, metaf2xml will split BUFR messages with multiple observations (i.e. taken at different times) and generate one report per observation. Therefore the callback function configured via start_cb() will possibly be called with data from more than one report during one call of parse_report() or process_bufr(). If the callback function does not process the data immediately (or at the latest at the end of a report) it needs to be made capable of storing multiple reports which need to be processed after parse_report()/process_bufr() finish.