CLEANUP: connection: rename all occurrences of stconn "cs" to "sc"

Function arguments and local variables called "cs" were renamed to "sc"
to avoid future confusion.
diff --git a/include/haproxy/connection-t.h b/include/haproxy/connection-t.h
index 87941eb..5e10722 100644
--- a/include/haproxy/connection-t.h
+++ b/include/haproxy/connection-t.h
@@ -389,19 +389,19 @@
 struct mux_ops {
 	int  (*init)(struct connection *conn, struct proxy *prx, struct session *sess, struct buffer *input);  /* early initialization */
 	int  (*wake)(struct connection *conn);        /* mux-layer callback to report activity, mandatory */
-	size_t (*rcv_buf)(struct stconn *cs, struct buffer *buf, size_t count, int flags); /* Called from the upper layer to get data */
-	size_t (*snd_buf)(struct stconn *cs, struct buffer *buf, size_t count, int flags); /* Called from the upper layer to send data */
-	int  (*rcv_pipe)(struct stconn *cs, struct pipe *pipe, unsigned int count); /* recv-to-pipe callback */
-	int  (*snd_pipe)(struct stconn *cs, struct pipe *pipe); /* send-to-pipe callback */
-	void (*shutr)(struct stconn *cs, enum co_shr_mode);     /* shutr function */
-	void (*shutw)(struct stconn *cs, enum co_shw_mode);     /* shutw function */
+	size_t (*rcv_buf)(struct stconn *sc, struct buffer *buf, size_t count, int flags); /* Called from the upper layer to get data */
+	size_t (*snd_buf)(struct stconn *sc, struct buffer *buf, size_t count, int flags); /* Called from the upper layer to send data */
+	int  (*rcv_pipe)(struct stconn *sc, struct pipe *pipe, unsigned int count); /* recv-to-pipe callback */
+	int  (*snd_pipe)(struct stconn *sc, struct pipe *pipe); /* send-to-pipe callback */
+	void (*shutr)(struct stconn *sc, enum co_shr_mode);     /* shutr function */
+	void (*shutw)(struct stconn *sc, enum co_shw_mode);     /* shutw function */
 
 	int (*attach)(struct connection *conn, struct sedesc *, struct session *sess); /* attach a stconn to an outgoing connection */
 	struct stconn *(*get_first_sc)(const struct connection *); /* retrieves any valid stconn from this connection */
 	void (*detach)(struct sedesc *); /* Detach an stconn from the stdesc from an outgoing connection, when the request is done */
 	int (*show_fd)(struct buffer *, struct connection *); /* append some data about connection into chunk for "show fd"; returns non-zero if suspicious */
-	int (*subscribe)(struct stconn *cs, int event_type,  struct wait_event *es); /* Subscribe <es> to events, such as "being able to send" */
-	int (*unsubscribe)(struct stconn *cs, int event_type,  struct wait_event *es); /* Unsubscribe <es> from events */
+	int (*subscribe)(struct stconn *sc, int event_type,  struct wait_event *es); /* Subscribe <es> to events, such as "being able to send" */
+	int (*unsubscribe)(struct stconn *sc, int event_type,  struct wait_event *es); /* Unsubscribe <es> from events */
 	int (*avail_streams)(struct connection *conn); /* Returns the number of streams still available for a connection */
 	int (*avail_streams_bidi)(struct connection *conn); /* Returns the number of bidirectional streams still available for a connection */
 	int (*avail_streams_uni)(struct connection *conn); /* Returns the number of unidirectional streams still available for a connection */
diff --git a/src/connection.c b/src/connection.c
index 6bd238a..620ef97 100644
--- a/src/connection.c
+++ b/src/connection.c
@@ -61,7 +61,7 @@
 {
 	if (conn_is_back(conn)) {
 		struct server *srv;
-		struct stconn *cs = conn->ctx;
+		struct stconn *sc = conn->ctx;
 		struct session *sess = conn->owner;
 
 		if (conn->flags & CO_FL_ERROR)
@@ -91,7 +91,7 @@
 		return 0;
 fail:
 		/* let the upper layer know the connection failed */
-		cs->app_ops->wake(cs);
+		sc->app_ops->wake(sc);
 		return -1;
 	} else
 		return conn_complete_session(conn);
@@ -1170,13 +1170,13 @@
 	 * we've sent the whole proxy line. Otherwise we use connect().
 	 */
 	if (conn->send_proxy_ofs) {
-		struct stconn *cs;
+		struct stconn *sc;
 		int ret;
 
 		/* If there is no mux attached to the connection, it means the
 		 * connection context is a stream connector.
 		 */
-		cs = conn->mux ? conn_get_first_sc(conn) : conn->ctx;
+		sc = conn->mux ? conn_get_first_sc(conn) : conn->ctx;
 
 		/* The target server expects a PROXY line to be sent first.
 		 * If the send_proxy_ofs is negative, it corresponds to the
@@ -1188,11 +1188,11 @@
 		 * send a LOCAL line (eg: for use with health checks).
 		 */
 
-		if (cs && sc_strm(cs)) {
+		if (sc && sc_strm(sc)) {
 			ret = make_proxy_line(trash.area, trash.size,
 					      objt_server(conn->target),
-					      sc_conn(sc_opposite(cs)),
-					      __sc_strm(cs));
+					      sc_conn(sc_opposite(sc)),
+					      __sc_strm(sc));
 		}
 		else {
 			/* The target server expects a LOCAL line to be sent first. Retrieving