patch 8.0.1376: cursor in terminal not always updated

Problem:    Cursor in terminal not always updated.
Solution:   Call gui_mch_flush(). (Ken Takata)
diff --git a/src/terminal.c b/src/terminal.c
index 5a2ebf8..744b7de 100644
--- a/src/terminal.c
+++ b/src/terminal.c
@@ -675,7 +675,10 @@
 	out_flush();
 #ifdef FEAT_GUI
 	if (gui.in_use)
+	{
 	    gui_update_cursor(FALSE, FALSE);
+	    gui_mch_flush();
+	}
 #endif
     }
 }