ospf6d/ospfd: refactor some common defines

Rearranging common defs and structures for use betweeen OSPFv2 and
OSPFv3.  Created a new file called libospf.h under lib directory to
hold defines that are common between OSPFv2 and OSPFv3 code bases.

[DL: split of defines refactor from timer refactor]
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
diff --git a/ospf6d/ospf6_interface.c b/ospf6d/ospf6_interface.c
index 40cda24..467479b 100644
--- a/ospf6d/ospf6_interface.c
+++ b/ospf6d/ospf6_interface.c
@@ -112,9 +112,9 @@
   oi->transdelay = OSPF6_INTERFACE_TRANSDELAY;
   oi->priority = OSPF6_INTERFACE_PRIORITY;
 
-  oi->hello_interval = OSPF6_INTERFACE_HELLO_INTERVAL;
-  oi->dead_interval = OSPF6_INTERFACE_DEAD_INTERVAL;
-  oi->rxmt_interval = OSPF6_INTERFACE_RXMT_INTERVAL;
+  oi->hello_interval = OSPF_HELLO_INTERVAL_DEFAULT;
+  oi->dead_interval = OSPF_ROUTER_DEAD_INTERVAL_DEFAULT;
+  oi->rxmt_interval = OSPF_RETRANSMIT_INTERVAL_DEFAULT;
   oi->cost = OSPF6_INTERFACE_COST;
   oi->state = OSPF6_INTERFACE_DOWN;
   oi->flag = 0;