support Directory Reference

Files
file	find_l2_flat_with.hpp [code]
file	find_l2_wide_with.hpp [code]
file	flat_rank.hpp [code]
file	flat_rank_select.hpp [code]
file	l12_type.hpp [code]
file	optimized_for.hpp [code]
file	popcount.hpp [code]
file	rank.hpp [code]
file	rank_select.hpp [code]
file	select.hpp [code]
file	wide_rank.hpp [code]
file	wide_rank_select.hpp [code]