patch 8.2.0622: Haiku: GUI does not compile

Problem:    Haiku: GUI does not compile.
Solution:   Various fixes. (Emir Sari, closes #5961)
diff --git a/src/proto/gui_haiku.pro b/src/proto/gui_haiku.pro
index 4d4c7d3..f392233 100644
--- a/src/proto/gui_haiku.pro
+++ b/src/proto/gui_haiku.pro
@@ -6,7 +6,7 @@
 void gui_mch_exit(int vim_exitcode);
 int gui_mch_init_check(void);
 void gui_mch_flush(void);
-
+int gui_mch_is_blink_off(void);
 void gui_mch_new_colors(void);
 void gui_mch_set_bg_color(guicolor_T color);
 void gui_mch_set_fg_color(guicolor_T color);