* target.h (target_signal_to_string): Make return type const char *.

	* target.h (target_signal_to_string): Make return type const char *.
	(target_signal_to_name): Ditto.
	(target_signal_from_name): Make arg const char *.
	* thread-db.c (thread_db_err_str): Make return type const char *.
	* utils.c (perror_with_name): Make arg const char *.
	* infrun.c (sig_print_info): Update.

	* signals/signals.c (signals): Make array and struct members const.
	(target_signal_to_string): Make return type const char *.
	(target_signal_to_name): Ditto.
	(target_signal_from_name): Make arg const char *.

	* gdbserver/gdbreplay.c (perror_with_name): Make arg const char *.
	* gdbserver/server.h (target_signal_to_name): Make return type
	const char *.