lib, bgpd: Fixup afi_t to be an enum and cleanup zebra.h

This code change does two things:

1) Removes ZEBRA_AFI_XXX #defines since they were redundant information
2) Switches afi_t to an enumerated type so that the compiler
can do a bit more compile time checking.

Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>
diff --git a/bgpd/bgp_routemap.c b/bgpd/bgp_routemap.c
index 20bf2eb..7555ca7 100644
--- a/bgpd/bgp_routemap.c
+++ b/bgpd/bgp_routemap.c
@@ -2383,14 +2383,12 @@
     {
       for (i = 0; i < ZEBRA_ROUTE_MAX; i++)
 	{
-	  if (bgp->rmap[ZEBRA_FAMILY_IPV4][i].name)
-	    bgp->rmap[ZEBRA_FAMILY_IPV4][i].map = 
-	      route_map_lookup_by_name (bgp->rmap[ZEBRA_FAMILY_IPV4][i].name);
-#ifdef HAVE_IPV6
-	  if (bgp->rmap[ZEBRA_FAMILY_IPV6][i].name)
-	    bgp->rmap[ZEBRA_FAMILY_IPV6][i].map =
-	      route_map_lookup_by_name (bgp->rmap[ZEBRA_FAMILY_IPV6][i].name);
-#endif /* HAVE_IPV6 */
+	  if (bgp->rmap[AFI_IP][i].name)
+	    bgp->rmap[AFI_IP][i].map =
+	      route_map_lookup_by_name (bgp->rmap[AFI_IP][i].name);
+	  if (bgp->rmap[AFI_IP6][i].name)
+	    bgp->rmap[AFI_IP6][i].map =
+	      route_map_lookup_by_name (bgp->rmap[AFI_IP][i].name);
 	}
     }
 }