Don't include libbfd.h outside of bfd, part 5

A rewrite of the code in bucomm.c supporting objdump -i, to use
bfd_iterate_over_targets rather than accessing bfd_target_vector
directly.  Calculates widest arch string rather than using an
out of date constant.  Stashes info from the first display of valid
target/arch combinations for use in second tabular display.

binutils/
	* bucomm.c: Don't include libbfd.h.
	(endian_string, display_target_list): Delete forward declaration.
	(display_info_table, display_target_tables): Likewise.
	(LONGEST_ARCH): Delete.
	(struct display_target): New.
	(do_display_target): New function.
	(display_target_list, display_info): Rewrite functions.
	(display_info_table): Delete.
	(do_info_size, do_info_header, do_info_row): New functions.