Requires libpri-1.4.12_beta1 or newer!
Completely untested, AOC-S/D/E ChargingRequest operations are sent to NT (DTAG BRI PTMP),
but rejected with "Unrecognized Operation".

NOTE: FreeTDM core needs support for this to be useful!
      Only AOC-E events are decoded and sent to the log.

To enable:
    Set (or add) <param name="opts" value="aoc"> in your
    libpri_spans span config.
Signed-off-by: Stefan Knoblich <s.knoblich@axsentis.de>