[REORG] session: move the data_ctx struct to the stream interface's applet

This is in fact where those parts belong to. The old data_state was replaced
by applet.state and is now initialized when the applet is registered. It's
worth noting that the applet does not need to know the session nor the
buffer anymore since everything is brought by the stream interface.

It is possible that having a separate applet struct would simplify the
code but that's not a big deal.
diff --git a/include/proto/dumpstats.h b/include/proto/dumpstats.h
index 3f89116..89e656e 100644
--- a/include/proto/dumpstats.h
+++ b/include/proto/dumpstats.h
@@ -27,7 +27,7 @@
 #include <types/buffers.h>
 #include <types/session.h>
 
-/* Flags for session->data_ctx.stats.flags */
+/* Flags for applet.ctx.stats.flags */
 #define STAT_FMT_CSV    0x00000001	/* dump the stats in CSV format instead of HTML */
 #define STAT_SHOW_STAT  0x00000002	/* dump the stats part */
 #define STAT_SHOW_INFO  0x00000004	/* dump the info part */
diff --git a/include/proto/proto_http.h b/include/proto/proto_http.h
index 417d5e6..a2d91ff 100644
--- a/include/proto/proto_http.h
+++ b/include/proto/proto_http.h
@@ -81,7 +81,7 @@
 void manage_client_side_cookies(struct session *t, struct buffer *req);
 void manage_server_side_cookies(struct session *t, struct buffer *rtr);
 void check_response_for_cacheability(struct session *t, struct buffer *rtr);
-int stats_check_uri(struct session *s, struct proxy *backend);
+int stats_check_uri(struct stream_interface *si, struct http_txn *txn, struct proxy *backend);
 void init_proto_http();
 int http_find_header2(const char *name, int len,
 		      char *sol, struct hdr_idx *idx,