[MEDIUM] default-server support

This patch implements default-server support allowing to change
default server options. It can be used in [defaults] or [backend]/[listen]
sections. Currently the following options are supported:

 - error-limit
 - fall
 - inter
 - fastinter
 - downinter
 - maxconn
 - maxqueue
 - minconn
 - on-error
 - port
 - rise
 - slowstart
 - weight
diff --git a/include/types/proxy.h b/include/types/proxy.h
index 6130cf5..78449e7 100644
--- a/include/types/proxy.h
+++ b/include/types/proxy.h
@@ -166,7 +166,7 @@
 		struct list inspect_rules;      /* inspection rules */
 	} tcp_req;
 	int acl_requires;                       /* Elements required to satisfy all ACLs (ACL_USE_*) */
-	struct server *srv;			/* known servers */
+	struct server *srv, defsrv;		/* known servers; default server configuration */
 	int srv_act, srv_bck;			/* # of servers eligible for LB (UP|!checked) AND (enabled+weight!=0) */
 	struct lbprm lbprm;			/* load-balancing parameters */
 	char *cookie_domain;			/* domain used to insert the cookie */