PR 11061

	PR 11061
	* output.h (class Output_reloc) [SHT_RELA]: Add is_relative
	function.
	(class Output_data_reloc_generic): Define.
	(class Output_data_reloc_base): Change base class to
	Output_data_reloc_generic.  Change add() method to call
	bump_relative_reloc_count for a relative reloc.  Remove
	sort_relocs_ field.
	* output.cc (Output_data_reloc_base::do_write): Change sort_reloc_
	to sort_relocs().
	* layout.cc (Layout::add_target_dynamic_tags): Change dyn_rel to
	Output_data_reloc_generic*.  Add DT_RELCOUNT/DT_RELACOUNT tag if
	appropriate.
	* layout.h (class Layout): Update declaration.