refactor constify most of rb_method_entry_t

Now that we have eliminated most destructive operations over the
rb_method_entry_t / rb_callable_method_entry_t, let's make them
mostly immutabe and mark them const.

One exception is rb_export_method(), which destructively modifies
visibilities of method entries.  I have left that operation as is
because I suspect that destructiveness is the nature of that
function.

1 files changed, 1 insertions, 1 deletions

diff --git a/gc.c b/gc.c
index 0caee4c260..52b3a66b6c 100644
--- a/gc.c
+++ b/gc.c
@@ -7829,7 +7829,7 @@ void rb_update_st_references(struct st_table *ht)
 }
 
 static void
-gc_ref_update_method_entry(rb_objspace_t *objspace, rb_method_entry_t *me)
+gc_ref_update_method_entry(rb_objspace_t *objspace, const rb_method_entry_t *me)
 {
     const rb_method_definition_t *def = me->def;