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/lib/zebra.h b/lib/zebra.h
index a607437..a9c76c6 100644
--- a/lib/zebra.h
+++ b/lib/zebra.h
@@ -445,11 +445,6 @@
 
 extern const char *zserv_command_string (unsigned int command);
 
-/* Zebra's family types. */
-#define ZEBRA_FAMILY_IPV4                1
-#define ZEBRA_FAMILY_IPV6                2
-#define ZEBRA_FAMILY_MAX                 3
-
 /* Error codes of zebra. */
 #define ZEBRA_ERR_NOERROR                0
 #define ZEBRA_ERR_RTEXIST               -1
@@ -483,9 +478,11 @@
 #endif
 
 /* Address family numbers from RFC1700. */
-#define AFI_IP                    1
-#define AFI_IP6                   2
-#define AFI_MAX                   3
+typedef enum {
+  AFI_IP  = 1,
+  AFI_IP6 = 2,
+#define AFI_MAX 3
+} afi_t;
 
 /* Subsequent Address Family Identifier. */
 #define SAFI_UNICAST              1
@@ -516,8 +513,6 @@
 #define SET_FLAG(V,F)        (V) |= (F)
 #define UNSET_FLAG(V,F)      (V) &= ~(F)
 
-/* AFI and SAFI type. */
-typedef u_int16_t afi_t;
 typedef u_int8_t safi_t;
 
 /* Zebra types. Used in Zserv message header. */