comms/fldigi: Update to 4.1.21

    Version 4.1.21
      * Maintenance release
        . many changes, refer to git log

    IPC log report
      * change logging date report to date ON vice date OFF

    xmlrpc methods
      * add new methods all data in ADIF 3.1.2 compliant format
        . logbook.last_record
        . logbook.all_records
      * add new methods as ADIF 3.1.2 compliant strings
        . modem.get_mode
        . modem.get_submode
      * add new date-time methods
        . log.get_time_on
        . log.get_date_on
        . log.get_time_off
        . log.get_date_off
        date-time correctly synchronized and in ZULU time