MINOR: conn-stream: Move some CS flags to the endpoint

Some CS flags, only related to the endpoint, are moved into the endpoint
struct. More will probably moved later. Those ones are not critical. So it
is pretty safe to move them now and this will ease next changes.
diff --git a/src/mux_h2.c b/src/mux_h2.c
index 7e7bc66..82196e9 100644
--- a/src/mux_h2.c
+++ b/src/mux_h2.c
@@ -1605,7 +1605,7 @@
 	cs = cs_new();
 	if (!cs)
 		goto out_close;
-	cs->flags |= CS_FL_NOT_FIRST;
+	cs->endp->flags |= CS_EP_NOT_FIRST;
 	cs_attach_endp_mux(cs, h2s, h2c->conn);
 	h2s->cs = cs;
 	h2c->nb_cs++;
@@ -1614,7 +1614,7 @@
 	 * be refine.
 	 */
 	if (flags & H2_SF_EXT_CONNECT_RCVD)
-		cs->flags |= CS_FL_WEBSOCKET;
+		cs->endp->flags |= CS_EP_WEBSOCKET;
 
 	/* The stream will record the request's accept date (which is either the
 	 * end of the connection's or the date immediately after the previous
@@ -4083,7 +4083,7 @@
 
 		while (node) {
 			h2s = container_of(node, struct h2s, by_id);
-			if (h2s->cs && h2s->cs->flags & CS_FL_WAIT_FOR_HS)
+			if (h2s->cs && h2s->cs->endp->flags & CS_EP_WAIT_FOR_HS)
 				h2s_notify_recv(h2s);
 			node = eb32_next(node);
 		}
@@ -4671,7 +4671,7 @@
 	struct h2s *h2s = __cs_mux(cs);
 
 	TRACE_ENTER(H2_EV_STRM_SHUT, h2s->h2c->conn, h2s);
-	if (cs->flags & CS_FL_KILL_CONN)
+	if (cs->endp->flags & CS_EP_KILL_CONN)
 		h2s->flags |= H2_SF_KILL_CONN;
 
 	if (mode)
@@ -4686,7 +4686,7 @@
 	struct h2s *h2s = __cs_mux(cs);
 
 	TRACE_ENTER(H2_EV_STRM_SHUT, h2s->h2c->conn, h2s);
-	if (cs->flags & CS_FL_KILL_CONN)
+	if (cs->endp->flags & CS_EP_KILL_CONN)
 		h2s->flags |= H2_SF_KILL_CONN;
 
 	h2_do_shutw(h2s);
@@ -5325,7 +5325,7 @@
 			break;
 	}
 
-	if (!h2s->cs || h2s->cs->flags & CS_FL_SHW) {
+	if (!h2s->cs || h2s->cs->endp->flags & CS_EP_SHW) {
 		/* Response already closed: add END_STREAM */
 		es_now = 1;
 	}
@@ -5745,7 +5745,7 @@
 			break;
 	}
 
-	if (!h2s->cs || h2s->cs->flags & CS_FL_SHW) {
+	if (!h2s->cs || h2s->cs->endp->flags & CS_EP_SHW) {
 		/* Request already closed: add END_STREAM */
 		es_now = 1;
 	}