REORG: connection: rename app_cb "data"

Now conn->data will designate the data layer which is the client for
the transport layer. In practice it's the stream interface and will
soon also be the health checks.
diff --git a/include/proto/connection.h b/include/proto/connection.h
index 17bef9b..f43525f 100644
--- a/include/proto/connection.h
+++ b/include/proto/connection.h
@@ -412,14 +412,14 @@
 	conn->flags |= CO_FL_ADDR_TO_SET;
 }
 
-/* prepares a connection with the appropriate app_cb, ctrl and transport layers.
+/* prepares a connection with the appropriate data, ctrl and transport layers.
  * The data state and context are set to 0, and the connection's owner is set.
  */
-static inline void conn_prepare(struct connection *conn, const struct app_cb *app,
+static inline void conn_prepare(struct connection *conn, const struct data_cb *data,
                                 const struct protocol *ctrl, const struct xprt_ops *xprt,
                                 void *owner)
 {
-	conn->app_cb = app;
+	conn->data = data;
 	conn->ctrl = ctrl;
 	conn->xprt = xprt;
 	conn->owner = owner;
diff --git a/include/proto/stream_interface.h b/include/proto/stream_interface.h
index cbaa966..3472b99 100644
--- a/include/proto/stream_interface.h
+++ b/include/proto/stream_interface.h
@@ -46,7 +46,7 @@
 extern struct si_ops si_embedded_ops;
 extern struct si_ops si_task_ops;
 extern struct si_ops si_conn_ops;
-extern struct app_cb si_conn_cb;
+extern struct data_cb si_conn_cb;
 
 struct task *stream_int_register_handler(struct stream_interface *si,
 					 struct si_applet *app);
diff --git a/include/types/connection.h b/include/types/connection.h
index 9215fa8..c289efa 100644
--- a/include/types/connection.h
+++ b/include/types/connection.h
@@ -169,14 +169,14 @@
 	int  (*init)(struct connection *conn);      /* initialize the transport layer */
 };
 
-/* app_cb describes the data layer's recv and send callbacks which are called
+/* data_cb describes the data layer's recv and send callbacks which are called
  * when I/O activity was detected after the transport layer is ready. These
  * callbacks are supposed to make use of the xprt_ops above to exchange data
  * from/to buffers and pipes.
  */
-struct app_cb {
-	void (*recv)(struct connection *conn);  /* application-layer recv callback */
-	void (*send)(struct connection *conn);  /* application-layer send callback */
+struct data_cb {
+	void (*recv)(struct connection *conn);  /* data-layer recv callback */
+	void (*send)(struct connection *conn);  /* data-layer send callback */
 };
 
 /* a target describes what is on the remote side of the connection. */
@@ -202,7 +202,7 @@
 struct connection {
 	const struct xprt_ops *xprt;  /* operations at the transport layer */
 	const struct protocol *ctrl;  /* operations at the socket layer */
-	const struct app_cb *app_cb;  /* application layer callbacks */
+	const struct data_cb  *data;  /* data layer callbacks */
 	void *owner;                  /* pointer to upper layer's entity (eg: stream interface) */
 	union {                       /* definitions which depend on connection type */
 		struct {              /*** information used by socket-based connections ***/
diff --git a/src/connection.c b/src/connection.c
index 8966bf7..07225e9 100644
--- a/src/connection.c
+++ b/src/connection.c
@@ -78,11 +78,11 @@
 	/* The data transfer starts here and stops on error and handshakes */
 	if ((fdtab[fd].ev & (FD_POLL_IN | FD_POLL_HUP | FD_POLL_ERR)) &&
 	    !(conn->flags & (CO_FL_WAIT_RD|CO_FL_WAIT_ROOM|CO_FL_ERROR|CO_FL_HANDSHAKE)))
-		conn->app_cb->recv(conn);
+		conn->data->recv(conn);
 
 	if ((fdtab[fd].ev & (FD_POLL_OUT | FD_POLL_ERR)) &&
 	    !(conn->flags & (CO_FL_WAIT_WR|CO_FL_WAIT_DATA|CO_FL_ERROR|CO_FL_HANDSHAKE)))
-		conn->app_cb->send(conn);
+		conn->data->send(conn);
 
 	if (unlikely(conn->flags & CO_FL_ERROR))
 		goto leave;
diff --git a/src/stream_interface.c b/src/stream_interface.c
index 625ca73..faeddde 100644
--- a/src/stream_interface.c
+++ b/src/stream_interface.c
@@ -66,7 +66,7 @@
 	.chk_snd = stream_int_chk_snd_conn,
 };
 
-struct app_cb si_conn_cb = {
+struct data_cb si_conn_cb = {
 	.recv    = si_conn_recv_cb,
 	.send    = si_conn_send_cb,
 };