[GOLD] Power10 stub selection

[GOLD] Power10 stub selection

gold version of commit e10a07b32dc1.

	* options.h (DEFINE_enum): Add optional_arg__ param, adjust
	all uses.
	(General_options): Add --power10-stubs and --no-power10-stubs.
	* options.cc (General_options::finalize): Handle --power10-stubs.
	* powerpc.cc (set_power10_stubs): Don't set when --power10-stubs=no.
	(power10_stubs_auto): New.
	(struct Plt_stub_ent): Add toc_ and tocoff_.  Don't use a bitfield
	for indx_.
	(struct Branch_stub_ent): Add toc_and tocoff_.  Use bitfields for
	iter_, notoc_ and save_res_.
	(add_plt_call_entry): Set toc_.  Adjust resizing conditions for
	--power10-stubs=auto.
	(add_long_branch_entry): Set toc_.
	(add_eh_frame, define_stub_syms): No longer use const_iterators
	for plt and long branch stub iteration.
	(build_tls_opt_head, build_tls_opt_tail): Change parameters and
	return value.  Move tests for __tls_get_addr to callers.
	(plt_call_size): Handle --power10-stubs=auto.
	(branch_stub_size): Likewise.
	(Stub_table::do_write): Likewise.
	(relocate): Likewise.