Implement QoS framework.

ovs-vswitchd doesn't declare its QoS capabilities in the database yet,
so the controller has to know what they are.  We can add that later.

The linux-htb QoS class has been tested to the extent that I can see that
it sets up the queues I expect when I run "tc qdisc show" and "tc class
show".  I haven't tested that the effects on flows are what we expect them
to be.  I am sure that there will be problems in that area that we will
have to fix.

lib/ofp-util.h

@@ -18,6 +18,7 @@
 #define OFP_UTIL_H 1
 
 #include <assert.h>
+#include <stdbool.h>
 #include <stddef.h>
 #include <stdint.h>
 #include "flow.h"
@@ -77,6 +78,7 @@ const union ofp_action *actions_first(struct actions_iterator *,
 const union ofp_action *actions_next(struct actions_iterator *);
 int validate_actions(const union ofp_action *, size_t n_actions,
                      int max_ports);
+bool action_outputs_to_port(const union ofp_action *, uint16_t port);
 
 void normalize_match(struct ofp_match *);