*: 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/ospf_routemap.c b/ospfd/ospf_routemap.c
index 7bd6c3d..f044e38 100644
--- a/ospfd/ospf_routemap.c
+++ b/ospfd/ospf_routemap.c
@@ -422,7 +422,7 @@
 route_match_tag (void *rule, struct prefix *prefix,
                  route_map_object_t type, void *object)
 {
-  u_short *tag;
+  route_tag_t *tag;
   struct external_info *ei;
 
   if (type == RMAP_OSPF)
@@ -440,8 +440,8 @@
 static void *
 route_match_tag_compile (const char *arg)
 {
-  u_short *tag;
-  u_short tmp;
+  route_tag_t *tag;
+  route_tag_t tmp;
 
   /* tag value shoud be integer. */
   if (! all_digit (arg))
@@ -596,7 +596,7 @@
 route_set_tag (void *rule, struct prefix *prefix,
                route_map_object_t type, void *object)
 {
-  u_short *tag;
+  route_tag_t *tag;
   struct external_info *ei;
 
   if (type == RMAP_OSPF)
@@ -615,8 +615,8 @@
 static void *
 route_set_tag_compile (const char *arg)
 {
-  u_short *tag;
-  u_short tmp;
+  route_tag_t *tag;
+  route_tag_t tmp;
 
   /* tag value shoud be integer. */
   if (! all_digit (arg))