patch 8.2.3664: cannot adjust sign highlighting for 'cursorline'

Problem:    Cannot adjust sign highlighting for 'cursorline'.
Solution:   Add CursorLineSign and CursorLineFold highlight groups.
            (Gregory Anders, closes #9201)
diff --git a/src/structs.h b/src/structs.h
index 9e0f64e..d9d3e30 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -853,6 +853,7 @@
     char_u	*sat_text;
     int		sat_texthl;
     int		sat_linehl;
+    int		sat_culhl;
     int		sat_priority;
 } sign_attrs_T;