bgpd, lib: adopt afi_t and safi_t in several places

* bgpd/bgp_attr.c, bgpd/bgp_open.h, bgpd/bgp_route.c, lib/prefix.c,
  lib/prefix.h: Various integer types were being used where, if we
  had strict type checking, afi_t and safi_t would be required.

Signed-off-by: G.Balaji <balajig81@gmail.com>
(cherry picked from commit c8af35ffa2dc79ff7d7ff00b1b61f1f50a100ab6)
diff --git a/bgpd/bgp_attr.c b/bgpd/bgp_attr.c
index 3996afd..ae0dc88 100644
--- a/bgpd/bgp_attr.c
+++ b/bgpd/bgp_attr.c
@@ -1301,8 +1301,8 @@
 bgp_mp_reach_parse (struct peer *peer, bgp_size_t length, struct attr *attr,
 		    struct bgp_nlri *mp_update)
 {
-  u_int16_t afi;
-  u_char safi;
+  afi_t afi;
+  safi_t safi;
   bgp_size_t nlri_len;
   size_t start;
   int ret;
@@ -1436,8 +1436,8 @@
 		      struct bgp_nlri *mp_withdraw)
 {
   struct stream *s;
-  u_int16_t afi;
-  u_char safi;
+  afi_t afi;
+  safi_t safi;
   u_int16_t withdraw_len;
   int ret;