piggyback acks in message not supported

[hemna]

There is a bug in the aprslib parsing library that doesn't handle parsing out the acks in line number format here: https://github.com/rossengeorgiev/aprs-python/issues/58

This means aprsd will fail to properly parse out messages/commands when a user sends a message with {WW}AA format

└─[$] <> cat test-2.py
import aprslib
import pprint
msg = "KO4KWC-6>APRS,TCPIP*,qAC,T2MCI::KO4KWC-14:weather ve3kbr {22}AA"
packet = aprslib.parse(msg)
pprint.pprint(packet)

results in

└─[$] <> python test-2.py
{'addresse': 'KO4KWC-14',
 'format': 'message',
 'from': 'KO4KWC-6',
 'message_text': 'weather ve3kbr {22}AA',
 'path': ['TCPIP*', 'qAC', 'T2MCI'],
 'raw': 'KO4KWC-6>APRS,TCPIP*,qAC,T2MCI::KO4KWC-14:weather ve3kbr {22}AA',
 'to': 'APRS',
 'via': 'T2MCI'}