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  * bgp_attr_as4_path(): discard, superseded by bgp_attr_aspath()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
diff --git a/tests/aspath_test.c b/tests/aspath_test.c
index fb504f3..9e51e8d 100644
--- a/tests/aspath_test.c
+++ b/tests/aspath_test.c
@@ -649,7 +649,7 @@
       s = stream_new (len);
       stream_put (s, data, len);
     }
-  as = aspath_parse (s, len, use32bit);
+  as = aspath_parse (s, len, use32bit, 0);
   
   if (s)
     stream_free (s);