/usr/include/ is in libcwidget-dev 0.5.16-3.1ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/cwidget/
/usr/include/cwidget/config/
/usr/include/cwidget/config/colors.h
/usr/include/cwidget/config/column_definition.h
/usr/include/cwidget/config/keybindings.h
/usr/include/cwidget/generic/
/usr/include/cwidget/generic/threads/
/usr/include/cwidget/generic/threads/event_queue.h
/usr/include/cwidget/generic/threads/threads.h
/usr/include/cwidget/generic/util/
/usr/include/cwidget/generic/util/bool_accumulate.h
/usr/include/cwidget/generic/util/eassert.h
/usr/include/cwidget/generic/util/exception.h
/usr/include/cwidget/generic/util/ref_ptr.h
/usr/include/cwidget/generic/util/slotarg.h
/usr/include/cwidget/generic/util/ssprintf.h
/usr/include/cwidget/generic/util/transcode.h
/usr/include/cwidget/widgets/
/usr/include/cwidget/widgets/button.h
/usr/include/cwidget/widgets/bin.h
/usr/include/cwidget/widgets/center.h
/usr/include/cwidget/widgets/container.h
/usr/include/cwidget/widgets/editline.h
/usr/include/cwidget/widgets/menu.h
/usr/include/cwidget/widgets/layout_item.h
/usr/include/cwidget/widgets/label.h
/usr/include/cwidget/widgets/frame.h
/usr/include/cwidget/widgets/statuschoice.h
/usr/include/cwidget/widgets/scrollbar.h
/usr/include/cwidget/widgets/passthrough.h
/usr/include/cwidget/widgets/pager.h
/usr/include/cwidget/widgets/multiplex.h
/usr/include/cwidget/widgets/minibuf_win.h
/usr/include/cwidget/widgets/menubar.h
/usr/include/cwidget/widgets/widget.h
/usr/include/cwidget/widgets/tree.h
/usr/include/cwidget/widgets/table.h
/usr/include/cwidget/widgets/treeitem.h
/usr/include/cwidget/widgets/transient.h
/usr/include/cwidget/widgets/togglebutton.h
/usr/include/cwidget/widgets/subtree.h
/usr/include/cwidget/widgets/text_layout.h
/usr/include/cwidget/widgets/staticitem.h
/usr/include/cwidget/widgets/size_box.h
/usr/include/cwidget/widgets/stacked.h
/usr/include/cwidget/widgets/radiogroup.h
/usr/include/cwidget/columnify.h
/usr/include/cwidget/curses++.h
/usr/include/cwidget/dialogs.h
/usr/include/cwidget/fragment.h
/usr/include/cwidget/fragment_cache.h
/usr/include/cwidget/fragment_contents.h
/usr/include/cwidget/style.h
/usr/include/cwidget/toplevel.h