Add bfd_free_cached_info support to a.out backends.

	Add bfd_free_cached_info support to a.out backends.
	* aoutx.h (aout_get_external_symbols): Renamed from
	aout_link_get_symbols.  Read strings even if symbols have been
	read.  Store string size in obj_aout_string_size.
	(NAME(aout,slurp_symbol_table)): Call aout_get_external_symbols to
	read the symbols.  Allocate the cached symbols with malloc, not
	bfd_alloc.
	(NAME(aout,slurp_reloc_table)): Allocate the cached relocs with
	malloc, not bfd_alloc.
	(NAME(aout,bfd_free_cached_info)): New function; free cached
	symbols and relocs.
	* libaout.h (struct aoutdata): Add external_string_size field.
	(obj_aout_external_string_size): New accessor macro.
	(NAME(aout,close_and_cleanup)): Don't declare.
	(NAME(aout,bfd_free_cached_info)): Declare.
	(aout_32_close_and_cleanup): Don't define.
	(aout_64_close_and_cleanup): Don't define.
	* aout-target.h (MY_bfd_free_cached_info): If not already defined,
	define as NAME(aout,free_cached_info).
	(MY_close_and_cleanup): If not already defined, define as
	MY_bfd_free_cached_info.
	* aout-adobe.c (aout_32_close_and_cleanup): Define.
	(aout_32_bfd_free_cached_info): Don't define.
	* bout.c (aout_32_close_and_cleanup): Define.
	(aout_32_bfd_free_cached_info): Don't define.
	* hp300hpux.c (MY_bfd_free_cached_info): Define as bfd_true.
	(MY_close_and_cleanup): Don't define.
	* i386lynx.c (NAME(lynx,slurp_reloc_table)): Allocate the cached
	relocs with malloc, not bfd_alloc.
	* i386os9k.c (aout_32_close_and_cleanup): Define.
	(aout_32_bfd_free_cached_info): Don't define.