Refactor get/set_property to take the item as first argument

lily/ledger-line-engraver.cc

 /*
   This file is part of LilyPond, the GNU music typesetter.
 
   Copyright (C) 2004--2020 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 40 matching lines @@
 {
   span_ = 0;
 }
 
 void
 Ledger_line_engraver::start_spanner ()
 {
   assert (!span_);
 
   span_ = make_spanner ("LedgerLineSpanner", SCM_EOL);
-  span_->set_bound (LEFT, unsmob<Grob> (get_property ("currentCommandColumn")));
+  span_->set_bound (LEFT, unsmob<Grob> (get_property (this, "currentCommandColumn")));
 }
 
 void
 Ledger_line_engraver::stop_translation_timestep ()
 {
   if (span_)
     {
       for (vsize i = 0; i < ledgered_grobs_.size (); i++)
         {
-          if (!to_boolean (ledgered_grobs_[i]->get_property ("no-ledgers")))
+          if (!to_boolean (get_property (ledgered_grobs_[i], "no-ledgers")))
             Pointer_group_interface::add_grob (span_,
                                                ly_symbol2scm ("note-heads"),
                                                ledgered_grobs_[i]);
         }
     }
 
   ledgered_grobs_.clear ();
 }
 
 void
@@ skipping 10 matching lines @@
 Ledger_line_engraver::finalize ()
 {
   stop_spanner ();
 }
 
 void
 Ledger_line_engraver::stop_spanner ()
 {
   if (span_)
     {
-      span_->set_bound (RIGHT, unsmob<Grob> (get_property ("currentCommandColumn")));
+      span_->set_bound (RIGHT, unsmob<Grob> (get_property (this, "currentCommandColumn")));
       span_ = 0;
     }
 }
 
 void
 Ledger_line_engraver::acknowledge_staff_symbol (Grob_info s)
 {
   Spanner *sym = dynamic_cast<Spanner *> (s.grob ());
 
   if (!span_
@@ skipping 24 matching lines @@
 
                 /* create */
                 "LedgerLineSpanner ",
 
                 /* read */
                 "",
 
                 /* write */
                 ""
                );