* ext/dbm/dbm.c (fdbm_initialize): used for rb_sys_fail_str.

* ext/sdbm/init.c (fsdbm_initialize): ditto.

* ext/tk/tcltklib.c (lib_do_one_event_core): no effect.

* ext/tk/tkutil/tkutil.c (tk_eval_cmd, tk_get_eval_string): no
  effect if tail call optimized.

* ext/tk/tkutil/tkutil.c (cbsubst_table_setup): set to const.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@55127 b2dd03c8-39d4-4d8f-98ff-823fe69b080e