patch 8.1.0709: windows are updated for every added/deleted sign
Problem: Windows are updated for every added/deleted sign.
Solution: Do not call update_debug_sign(). Only redraw when the line with
the sign is visible. (idea from neovim #9479)
diff --git a/src/proto/screen.pro b/src/proto/screen.pro
index 665b772..2e5f2e0 100644
--- a/src/proto/screen.pro
+++ b/src/proto/screen.pro
@@ -5,6 +5,7 @@
void redraw_all_later(int type);
void redraw_curbuf_later(int type);
void redraw_buf_later(buf_T *buf, int type);
+void redraw_buf_line_later(buf_T *buf, linenr_T lnum);
void redraw_buf_and_status_later(buf_T *buf, int type);
int redraw_asap(int type);
void redraw_after_callback(int call_update_screen);