reuse reqid when a ROUTED child_sa gets INSTALLED

fixed a bug in retransmission code
added support for the "keyingtries" ipsec.conf parameter
added support for the "dpddelay" ipsec.conf parameter
done some work for "dpdaction" behavior
some other cleanups and fixes

src/charon/doc/Todo-list.txt

@@ -63,9 +63,12 @@
 - configure flag which allows to ommit vendor id in pluto
 - use dpdaction/dpddelay parameters from ipsec.conf
 - ikelifetime should optionally enforce reauthentication
+- cookies/DDoS prevention
 - implement a mechanism against thread exhaustion
   when a blocked IKE_SA receives a lot of messages
 - add a crl fetch mechanism which synchronizes equal fetches
 - add support for CERTREQs
 - use same reqid for routed connections when they are set up
+- if a CHILD_SA gets created, check if it is already ROUTED somewhere:
+  - remove that route and reuse reqid
 - add firewall script support