* core/line_info.hh: Rename hidden as is_hidden.

	* core/object_links.hh: Add duplicate().

	* filter/object_links_bbox_ratio.hh: Use object_links::duplicate.

	* debug/links_decision_image.hh,
	* src/debug/show_info_median_inter_characters.cc,
	* src/debug/show_info_x_height.cc,
	* src/debug/show_links_bbox_h_ratio.cc,
	* src/debug/show_links_left_right_links_validation.cc: Make
	compile again.

	* tests/unit_test/unit-tests.mk: Regen.

	* text/extract_lines.hh: Update with latest changes.

	* text/recognition.hh: Check whether a line is hidden or not.