MINOR: stick-tables: Add peers process binding computing.

Add a list of proxies for all the stick-tables (->proxies_list struct stktable
member) so that to be able to compute the process bindings of the peers after having
parsed the configuration file.
The proxies are added to the stick-tables they reference when parsing
stick-tables lines in proxy sections, when checking the actions in
check_trk_action() and when resolving samples args for stick-tables
without checking is they are duplicates. We check only there is no loop.
Then, after having parsed everything, we add the proxy bindings to the
peers frontend bindings with stick-tables they reference.
diff --git a/include/types/proxy.h b/include/types/proxy.h
index f6d2634..45ef2c8 100644
--- a/include/types/proxy.h
+++ b/include/types/proxy.h
@@ -395,6 +395,7 @@
 	struct conn_src conn_src;               /* connection source settings */
 	enum obj_type *default_target;		/* default target to use for accepted streams or NULL */
 	struct proxy *next;
+	struct proxy *next_stkt_ref;    /* Link to the list of proxies which refer to the same stick-table. */
 
 	struct list logsrvs;
 	struct list logformat; 			/* log_format linked list */
diff --git a/include/types/stick_table.h b/include/types/stick_table.h
index ff9546c..a4baeb3 100644
--- a/include/types/stick_table.h
+++ b/include/types/stick_table.h
@@ -185,6 +185,7 @@
 		void *p;
 	} data_arg[STKTABLE_DATA_TYPES]; /* optional argument of each data type */
 	struct proxy *proxy;      /* The proxy this stick-table is attached to, if any.*/
+	struct proxy *proxies_list; /* The list of proxies which reference this stick-table. */
 };
 
 extern struct stktable_data_type stktable_data_types[STKTABLE_DATA_TYPES];