patch 8.0.1450: GUI: endless loop when stopping cursor blinking

Problem:    Endless loop when gui_mch_stop_blink() is called while blink_state
            is BLINK_OFF. (zdohnal)
Solution:   Avoid calling gui_update_cursor() recursively.
diff --git a/src/gui_mac.c b/src/gui_mac.c
index 97cbf80..db9f959 100644
--- a/src/gui_mac.c
+++ b/src/gui_mac.c
@@ -5156,9 +5156,10 @@
  * Stop the cursor blinking.  Show the cursor if it wasn't shown.
  */
     void
-gui_mch_stop_blink(void)
+gui_mch_stop_blink(int may_call_gui_update_cursor)
 {
-    gui_update_cursor(TRUE, FALSE);
+    if (may_call_gui_update_cursor)
+	gui_update_cursor(TRUE, FALSE);
     /* TODO: TODO: TODO: TODO: */
 /*    gui_w32_rm_blink_timer();
     if (blink_state == BLINK_OFF)