lib: add SAFI_ENCAP type, safi2str prefix utility

Signed-off-by: Lou Berger <lberger@labn.net>
diff --git a/lib/zebra.h b/lib/zebra.h
index 5f45a3a..644729b 100644
--- a/lib/zebra.h
+++ b/lib/zebra.h
@@ -489,7 +489,8 @@
 #define SAFI_MULTICAST            2
 #define SAFI_RESERVED_3           3
 #define SAFI_MPLS_VPN             4
-#define SAFI_MAX                  5
+#define SAFI_ENCAP		  7 /* per IANA */
+#define SAFI_MAX                  8
 
 /* Default Administrative Distance of each protocol. */
 #define ZEBRA_KERNEL_DISTANCE_DEFAULT      0