Refactor get/set_property to take the item as first argument

lily/hara-kiri-group-spanner.cc

 /*
   This file is part of LilyPond, the GNU music typesetter.
 
   Copyright (C) 1998--2020 Jan Nieuwenhuizen <janneke@gnu.org>
   Han-Wen Nienhuys <hanwen@xs4all.nl>
 
   LilyPond is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.
@@ skipping 80 matching lines @@
   for (vsize i = 0; i < friends.size (); ++i)
     if (friends[i]->is_live () && !request_suicide_alone (friends[i], start, end))
       return false;
 
   return true;
 }
 
 bool
 Hara_kiri_group_spanner::request_suicide_alone (Grob *me, vsize start, vsize end)
 {
-  if (!to_boolean (me->get_property ("remove-empty")))
+  if (!to_boolean (get_property (me, "remove-empty")))
     return false;
 
-  bool remove_first = to_boolean (me->get_property ("remove-first"));
+  bool remove_first = to_boolean (get_property (me, "remove-first"));
   if (!remove_first && start <= 0)
     return false;
 
-  SCM important = me->get_property ("important-column-ranks");
+  SCM important = get_property (me, "important-column-ranks");
   if (scm_is_vector (important))
     {
       vsize len = scm_c_vector_length (important);
       if (find_in_range (important, 0, len, start, end))
         return false;
     }
   else /* build the important-columns-cache */
     {
       extract_grob_set (me, "items-worth-living", worth);
       vector<int> ranks;
 
       for (vsize i = 0; i < worth.size (); i++)
         {
           Interval_t<int> iv = worth[i]->spanned_rank_interval ();
           for (int j = iv[LEFT]; j <= iv[RIGHT]; j++)
             ranks.push_back (j);
         }
       vector_sort (ranks, std::less<int> ());
       uniq (ranks);
 
       SCM scm_vec = scm_c_make_vector (ranks.size (), SCM_EOL);
       for (vsize i = 0; i < ranks.size (); i++)
         scm_c_vector_set_x (scm_vec, i, scm_from_int (ranks[i]));
-      me->set_property ("important-column-ranks", scm_vec);
+      set_property (me, "important-column-ranks", scm_vec);
 
       return request_suicide (me, start, end);
     }
 
   return true;
 }
 
 void
 Hara_kiri_group_spanner::consider_suicide (Grob *me)
 {
@@ skipping 57 matching lines @@
 
                /* properties */
                "items-worth-living "
                "important-column-ranks "
                "keep-alive-with "
                "make-dead-when "
                "remove-empty "
                "remove-first "
                "remove-layer "
               );