CLEANUP: mux-h1; Rename H1S_F_ERROR flag into H1S_F_ERROR_MASK

In fact, H1S_F_ERROR is not a flag but a mask. So rename it to make it
clear.
diff --git a/src/mux_h1.c b/src/mux_h1.c
index 27d915c..ac415fa 100644
--- a/src/mux_h1.c
+++ b/src/mux_h1.c
@@ -439,7 +439,7 @@
 		return 0;
 	}
 
-	if (h1c->h1s && (h1c->h1s->flags & H1S_F_ERROR)) {
+	if (h1c->h1s && (h1c->h1s->flags & H1S_F_ERROR_MASK)) {
 		TRACE_DEVEL("recv not allowed because of error on h1s", H1_EV_H1C_RECV|H1_EV_H1C_BLK, h1c->conn);
 		return 0;
 	}
@@ -836,7 +836,7 @@
 				H1C_F_ST_EMBRYONIC|H1C_F_ST_ATTACHED|H1C_F_ST_READY|
 				H1C_F_OUT_FULL|H1C_F_OUT_ALLOC|H1C_F_IN_SALLOC|
 				H1C_F_CO_MSG_MORE|H1C_F_CO_STREAMER);
-		if (h1s->flags & H1S_F_ERROR) {
+		if (h1s->flags & H1S_F_ERROR_MASK) {
 			h1c->flags |= H1C_F_ST_ERROR;
 			TRACE_ERROR("h1s on error, set error on h1c", H1_EV_H1S_END|H1_EV_H1C_ERR, h1c->conn, h1s);
 		}