bgpd: more SAFI fixes

Two macros resolving to the same integer constant broke a case block and
a more thorough merge of BGP_SAFI_VPNV4 and BGP_SAFI_VPNV6 was
performed.

* bgpd.h: MPLS-labeled VPN SAFI is AFI-independent, switch to single
* macro
* bgp_capability_test.c: update test data
* bgp_mp_attr_test.c: idem
* bgp_route.c: (bgp_maximum_prefix_overflow, bgp_table_stats_vty) update
  macro and check conditions (where appropriate)
* bgp_packet.c: (bgp_route_refresh_send, bgp_capability_send,
  bgp_update_receive, bgp_route_refresh_receive): idem
* bgp_open.c: (bgp_capability_vty_out, bgp_afi_safi_valid_indices,
  bgp_open_capability_orf, bgp_open_capability): idem
* bgp_attr.c: (bgp_mp_reach_parse, bgp_packet_attribute,
  bgp_packet_withdraw): idem
diff --git a/tests/bgp_mp_attr_test.c b/tests/bgp_mp_attr_test.c
index dde0df2..d6e9f0c 100644
--- a/tests/bgp_mp_attr_test.c
+++ b/tests/bgp_mp_attr_test.c
@@ -286,10 +286,10 @@
     SHOULD_ERR,
     AFI_IP, SAFI_UNICAST, VALID_AFI,
   },
-  { "IPv4-vpnv4",
-    "IPv4/VPNv4 MP Reach, RD, Nexthop, 3 NLRIs", 
+  { "IPv4-MLVPN",
+    "IPv4/MPLS-labeled VPN MP Reach, RD, Nexthop, 3 NLRIs", 
     {
-      /* AFI / SAFI */		0x0, AFI_IP, BGP_SAFI_VPNV4,
+      /* AFI / SAFI */		0x0, AFI_IP, SAFI_MPLS_LABELED_VPN,
       /* nexthop bytes */	12,
       /* RD */			0, 0, 1, 2,
                                 0, 0xff, 3, 4,
@@ -409,10 +409,10 @@
     SHOULD_ERR,
     AFI_IP, SAFI_UNICAST, VALID_AFI,
   },
-  { "IPv4-unreach-vpnv4",
-    "IPv4/VPNv4 MP Unreach, RD, 3 NLRIs", 
+  { "IPv4-unreach-MLVPN",
+    "IPv4/MPLS-labeled VPN MP Unreach, RD, 3 NLRIs", 
     {
-      /* AFI / SAFI */		0x0, AFI_IP, BGP_SAFI_VPNV4,
+      /* AFI / SAFI */		0x0, AFI_IP, SAFI_MPLS_LABELED_VPN,
       /* nexthop bytes */	12,
       /* RD */			0, 0, 1, 2,
                                 0, 0xff, 3, 4,