/usr/include/ is in libplumb2-dev 1.0.12~rc1+hg2777-1.2.
This file is owned by root:root, with mode 0o755.
..
/usr/include/clplumbing/
/usr/include/clplumbing/Gmain_timeout.h
/usr/include/clplumbing/cl_plugin.h
/usr/include/clplumbing/cl_uuid.h
/usr/include/clplumbing/cl_misc.h
/usr/include/clplumbing/longclock.h
/usr/include/clplumbing/cl_quorum.h
/usr/include/clplumbing/GSource.h
/usr/include/clplumbing/cl_syslog.h
/usr/include/clplumbing/GSource_internal.h
/usr/include/clplumbing/setproctitle.h
/usr/include/clplumbing/cl_quorumd.h
/usr/include/clplumbing/realtime.h
/usr/include/clplumbing/apphb_cs.h
/usr/include/clplumbing/cl_signal.h
/usr/include/clplumbing/md5.h
/usr/include/clplumbing/replytrack.h
/usr/include/clplumbing/cl_log.h
/usr/include/clplumbing/timers.h
/usr/include/clplumbing/cl_poll.h
/usr/include/clplumbing/coredumps.h
/usr/include/clplumbing/mkstemp_mode.h
/usr/include/clplumbing/cl_reboot.h
/usr/include/clplumbing/lsb_exitcodes.h
/usr/include/clplumbing/ipc.h
/usr/include/clplumbing/proctrack.h
/usr/include/clplumbing/cpulimits.h
/usr/include/clplumbing/cl_tiebreaker.h
/usr/include/clplumbing/cl_random.h
/usr/include/clplumbing/cl_pidfile.h
/usr/include/clplumbing/uids.h
/usr/include/clplumbing/netstring.h
/usr/include/clplumbing/base64.h
/usr/include/clplumbing/loggingdaemon.h