Convert auto-load.c to type-safe registry API

Convert auto-load.c to type-safe registry API

This changes auto-load.c to use the type-safe registry API.  It also
changes a couple of types to "bool", removing uses of "FALSE".

gdb/ChangeLog
2019-05-08  Tom Tromey  <tom@tromey.com>

	* auto-load.c (struct auto_load_pspace_info): Add destructor and
	initializers.
	<unsupported_script_warning_printed,
	script_not_found_warning_printed>: Now bool.
	(auto_load_pspace_data): Change type.
	(~auto_load_pspace_info): Rename from
	auto_load_pspace_data_cleanup.
	(get_auto_load_pspace_data, init_loaded_scripts_info)
	(clear_section_scripts, maybe_print_unsupported_script_warning)
	(maybe_print_script_not_found_warning, _initialize_auto_load):
	Update.