* gold/incremental.cc (Sized_incremental_binary::do_process_got_plt):

	* gold/incremental.cc (Sized_incremental_binary::do_process_got_plt):
	Use abstract base class for GOT.
	* gold/output.h (class Output_data_got_base): New abstract base class.
	(class Output_data_got): Derive from new base class, adjust ctors.
	(Output_data_got::reserve_slot): Make virtual; rename to
	do_reserve_slot; Adjust callers.
	* gold/target.h (Sized_target::init_got_plt_for_update): Return
	pointer to abstract base class.
	* gold/x86_64.cc (Target_x86_64::init_got_plt_for_update): Likewise.