[GOLD] Two GOT sections for PowerPC64

[GOLD] Two GOT sections for PowerPC64

Split .got into two piece, one with the header and entries for small
model got entries, the other with entries for medium/large model got
entries.  The idea is to better support mixed pcrel/non-pcrel code
where non-pcrel small-model .toc entries need to be within 32k of the
toc pointer.

	* target.h (Target::tls_offset_for_local): Add got param.
	(Target::tls_offset_for_global): Likewise.
	(Target::do_tls_offset_for_local, do_tls_offset_for_global): Likewise.
	* output.h (Output_data_got::Got_entry::write): Add got param.
	* output.cc (Output_data_got::Got_entry::write): Likewise, pass to
	tls_offset_for_local/global calls.
	(Output_data_got::do_write): Adjust to suit.
	* s390.cc (Target_s390::do_tls_offset_for_local): Likewise.
	(Target_s390::do_tls_offset_for_global): Likewise.
	* powerpc.cc (enum Got_type): Extend with small types, move from
	class Target_powerpc.
	(Target_powerpc::biggot_): New.
	(Traget_powerpc::do_tls_offset_for_local, do_tls_offset_for_global,
	got_size, got_section, got_base_offset): Handle biggot_.
	(Target_powerpc::do_define_standard_symbols): Adjust.
	(Target_powerpc::make_plt_section, do_finalize_sections): Likewise.
	(Output_data_got_powerpc::Output_data_got_powerpc): Only make
	64-bit header for small got section.
	(Output_data_got_powerpc::g_o_t): Only return a result for small
	got section.
	(Output_data_got_powerpc::write): Only write small got section
	header.
	(Target_powerpc::Scan::local, global): Select small/big Got_type
	and section to suit reloc.
	(Target_powerpc::Relocate::relocate): Similarly.
	(Sort_toc_sections): Rewrite.