*: Widen width of Zserv routing tag field.

* lib/zebra.h: Introduce a route_tag_t type for route tags generally,
  and make it 4 bytes wide - so it can directly hold things like an ASN, or
  the OSPF ASE-LSA tag.
* zebra/rib.h: Use route_tag_t instead of u_short.
* *: Update 'u_short (*)?(tag|tmp)' to use route_tag_t instead of u_short.
  Update stream_{get,put} to l instead of w.
* ospf_zebra.c: (ospf_zebra_add) test OSPF tag within range of ROUTE_TAG_MAX.
diff --git a/ospfd/ospfd.h b/ospfd/ospfd.h
index 4181d11..0315164 100644
--- a/ospfd/ospfd.h
+++ b/ospfd/ospfd.h
@@ -239,7 +239,7 @@
   } dmetric [ZEBRA_ROUTE_MAX + 1];
 
   /* Redistribute tag info. */
-  u_short dtag [ZEBRA_ROUTE_MAX + 1];
+  route_tag_t dtag [ZEBRA_ROUTE_MAX + 1];
 
   /* For redistribute route map. */
   struct