MEDIUM: peers: Fix a peer stick-tables synchronization issue.

During the stick-table teaching process which occurs at reloading/restart time,
expiration dates of stick-tables entries were not synchronized between peers.

This patch adds two new stick-table messages to provide such a synchronization feature.

As these new messages are not supported by older haproxy peers protocol versions,
this patch increments peers protol version, from 2.0 to 2.1, to help in detecting/supporting
such older peers protocol implementations so that new versions might still be able
to transparently communicate with a newer one.

[wt: technically speaking it would be nice to have this backported into 1.6
 as some people who reload often are affected by this design limitation, but
 it's not a totally transparent change that may make certain users feel
 reluctant to upgrade older versions. Let's let it cook in 1.7 first and
 decide later]
diff --git a/include/proto/stick_table.h b/include/proto/stick_table.h
index 8c97f73..941e2ff 100644
--- a/include/proto/stick_table.h
+++ b/include/proto/stick_table.h
@@ -42,6 +42,10 @@
 int stktable_parse_type(char **args, int *idx, unsigned long *type, size_t *key_size);
 struct stksess *stktable_get_entry(struct stktable *table, struct stktable_key *key);
 struct stksess *stktable_store(struct stktable *t, struct stksess *ts, int local);
+struct stksess *stktable_store_with_exp(struct stktable *t, struct stksess *ts,
+                                        int local, int expire);
+struct stksess *stktable_touch_with_exp(struct stktable *t, struct stksess *ts,
+                                        int local, int expire);
 struct stksess *stktable_touch(struct stktable *t, struct stksess *ts, int local);
 struct stksess *stktable_lookup(struct stktable *t, struct stksess *ts);
 struct stksess *stktable_lookup_key(struct stktable *t, struct stktable_key *key);