/usr/include/ is in audacious-dev 3.4.3-1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/x86_64-linux-gnu/
/usr/include/x86_64-linux-gnu/libaudcore/
/usr/include/x86_64-linux-gnu/libaudcore/audio.h
/usr/include/libaudgui/
/usr/include/libaudgui/libaudgui-gtk.h
/usr/include/libaudgui/libaudgui.h
/usr/include/libaudgui/list.h
/usr/include/audacious/
/usr/include/audacious/api-alias-end.h
/usr/include/audacious/misc.h
/usr/include/audacious/api-define-end.h
/usr/include/audacious/dbus-service.h
/usr/include/audacious/api.h
/usr/include/audacious/plugins.h
/usr/include/audacious/plugins-api.h
/usr/include/audacious/misc-api.h
/usr/include/audacious/playlist.h
/usr/include/audacious/api-alias-begin.h
/usr/include/audacious/debug.h
/usr/include/audacious/dbus.h
/usr/include/audacious/api-define-begin.h
/usr/include/audacious/drct.h
/usr/include/audacious/drct-api.h
/usr/include/audacious/preferences.h
/usr/include/audacious/plugin.h
/usr/include/audacious/playlist-api.h
/usr/include/audacious/i18n.h
/usr/include/audacious/audtag.h
/usr/include/audacious/types.h
/usr/include/audacious/audctrl.h
/usr/include/libaudcore/
/usr/include/libaudcore/vfs.h
/usr/include/libaudcore/index.h
/usr/include/libaudcore/core.h
/usr/include/libaudcore/tuple.h
/usr/include/libaudcore/hook.h
/usr/include/libaudcore/vfs_async.h
/usr/include/libaudcore/audstrings.h