Add support for registry scoped ASNs

[jwbensley]

Add support for parsing registry scoped ASNs such as RIPE::AS41695 to bgpq4.

Existing behaviour:

$ which bgpq4
/usr/bin/bgpq4

$ /usr/bin/bgpq4 -v
bgpq4 - a versatile utility to generate BGP filters
version: 1.4
website: https://github.com/bgp/bgpq4
maintainer: Job Snijders <job@sobornost.net>

# Without a source prefix all data sources are used:

$ /usr/bin/bgpq4 -d AS41695
DEBUG: expander.c:908 bgpq_expand Acquired sendbuf of 4608 bytes
DEBUG: expander.c:929 bgpq_expand Sending '!!' to server to request for the connection to remain open
DEBUG: expander.c:938 bgpq_expand b->identify: Sending '!n bgpq4 1.4' to server.
DEBUG: expander.c:951 bgpq_expand Got answer C
DEBUG: expander.c:397 bgpq_pipeline expander: sending !gas41695
no ip prefix-list NN
ip prefix-list NN permit 89.21.224.0/19
ip prefix-list NN permit 134.0.64.0/21

# Specifying a source prefix is not currently supported

$ /usr/bin/bgpq4 -d RIPE::AS41695
ERROR:Unable to parse prefix 'RIPE::AS41695', af=10 (inet6), ret=0
ERROR:Unable to parse prefix RIPE::AS41695
ERROR:Unable to add prefix RIPE::AS41695 (bad prefix or address-family)

PR behaviour:

# When no source prefix is specified, the server source is set to all (effectively no change)

$ ./bgpq4 -d AS41695
DEBUG: expander.c:1094 bgpq_expand Sending '!!' to server to request for the connection to remain open
DEBUG: expander.c:1104 bgpq_expand b->identify: Sending '!n bgpq4 1.16' to server.
DEBUG: expander.c:1118 bgpq_expand Got answer C
DEBUG: expander.c:457 bgpq_get_irrd_sources Requesting source list !s-lc
DEBUG: expander.c:468 bgpq_get_irrd_sources Got answer A127
NTTCOM,INTERNAL,LACNIC,RADB,RIPE,RIPE-NONAUTH,ALTDB,BELL,LEVEL3,APNIC,JPIRR,ARIN,BBOI,TC,AFRINIC,IDNIC,RPKI,REGISTROBR,CANARIE
C
DEBUG: expander.c:560 bgpq_pipeline expander: sending !sNTTCOM,INTERNAL,LACNIC,RADB,RIPE,RIPE-NONAUTH,ALTDB,BELL,LEVEL3,APNIC,JPIRR,ARIN,BBOI,TC,AFRINIC,IDNIC,RPKI,REGISTROBR,CANARIE
DEBUG: expander.c:835 bgpq_read No data expanding !sNTTCOM,INTERNAL,LACNIC,RADB,RIPE,RIPE-NONAUTH,ALTDB,BELL,LEVEL3,APNIC,JPIRR,ARIN,BBOI,TC,AFRINIC,IDNIC,RPKI,REGISTROBR,CANARIE
DEBUG: expander.c:560 bgpq_pipeline expander: sending !gas41695
no ip prefix-list NN
ip prefix-list NN permit 89.21.224.0/19
ip prefix-list NN permit 134.0.64.0/21


# When source prefix is specified, source is used:

$ ./bgpq4 -d RIPE::AS41695
DEBUG: expander.c:1094 bgpq_expand Sending '!!' to server to request for the connection to remain open
DEBUG: expander.c:1104 bgpq_expand b->identify: Sending '!n bgpq4 1.16' to server.
DEBUG: expander.c:1118 bgpq_expand Got answer C
DEBUG: expander.c:457 bgpq_get_irrd_sources Requesting source list !s-lc
DEBUG: expander.c:468 bgpq_get_irrd_sources Got answer A127
NTTCOM,INTERNAL,LACNIC,RADB,RIPE,RIPE-NONAUTH,ALTDB,BELL,LEVEL3,APNIC,JPIRR,ARIN,BBOI,TC,AFRINIC,IDNIC,RPKI,REGISTROBR,CANARIE
C
DEBUG: expander.c:560 bgpq_pipeline expander: sending !sNTTCOM,INTERNAL,LACNIC,RADB,RIPE,RIPE-NONAUTH,ALTDB,BELL,LEVEL3,APNIC,JPIRR,ARIN,BBOI,TC,AFRINIC,IDNIC,RPKI,REGISTROBR,CANARIE
DEBUG: expander.c:835 bgpq_read No data expanding !sNTTCOM,INTERNAL,LACNIC,RADB,RIPE,RIPE-NONAUTH,ALTDB,BELL,LEVEL3,APNIC,JPIRR,ARIN,BBOI,TC,AFRINIC,IDNIC,RPKI,REGISTROBR,CANARIE
DEBUG: expander.c:560 bgpq_pipeline expander: sending !sRIPE
DEBUG: expander.c:560 bgpq_pipeline expander: sending !gas41695
DEBUG: expander.c:835 bgpq_read No data expanding !sRIPE
no ip prefix-list NN
ip prefix-list NN permit 89.21.224.0/19
ip prefix-list NN permit 134.0.64.0/21

I've updated the unit tests to check this new functionality, and documented it the README.

[job]

Thanks! Will test a bit and then plan to merge