gold: Allow use_plt_offset to be specified for global relocations.

gold: Allow use_plt_offset to be specified for global relocations.

gold/

	* output.h (Output_reloc): Allow use_plt_offset for global relocs too.
	(class Output_data_reloc): Adjust calls to Output_reloc_type.
	(Output_data_reloc::add_global_relative): (RELA only) Add use_plt_offset.
	* output.cc (Output_reloc::Output_reloc): Add use_plt_offset flag for
	global relocs too.
	(Output_reloc::symbol_value): Respect use_plt_offset_ for global symbols.
	* powerpc.cc (Target_powerpc::Scan::global): Adjust add_global_relative
	calls.
	* sparc.cc (Target_sparc::Scan::global): Likewise.
	* x86_64.cc (Target_x86_64::Scan::global): Likewise.