bgpd: fix handling of AS path data
* bgpd/bgp_aspath.c
* assegments_parse(): add handling of AS4_PATH input, update bounds
checks, add check for AS segment type
* aspath_parse(): add handling of AS4_PATH input, expect
assegments_parse() to do length checking
* aspath_empty(): update for the new function prototype
* bgpd/bgp_aspath.h: ditto
* tests/aspath_test.c: ditto
* bgpd/bgp_attr.c
* bgp_attr_aspath(): add handling of AS4_PATH input, update flags
checks, change returned type
* bgp_attr_as4_path(): discard, superseded by bgp_attr_aspath()
* bgp_attr_parse(): update respectively
4 files changed