/usr/include/qhull/ is in libqhull-dev 2012.1-5.
This file is owned by root:root, with mode 0o755.
..
/usr/include/qhull/Coordinates.h
/usr/include/qhull/PointCoordinates.h
/usr/include/qhull/Qhull.h
/usr/include/qhull/QhullError.h
/usr/include/qhull/QhullFacet.h
/usr/include/qhull/QhullFacetList.h
/usr/include/qhull/QhullFacetSet.h
/usr/include/qhull/QhullHyperplane.h
/usr/include/qhull/QhullIterator.h
/usr/include/qhull/QhullLinkedList.h
/usr/include/qhull/QhullPoint.h
/usr/include/qhull/QhullPointSet.h
/usr/include/qhull/QhullPoints.h
/usr/include/qhull/QhullQh.h
/usr/include/qhull/QhullRidge.h
/usr/include/qhull/QhullSet.h
/usr/include/qhull/QhullSets.h
/usr/include/qhull/QhullStat.h
/usr/include/qhull/QhullVertex.h
/usr/include/qhull/QhullVertexSet.h
/usr/include/qhull/README
/usr/include/qhull/RboxPoints.h
/usr/include/qhull/RoadError.h
/usr/include/qhull/RoadLogEvent.h
/usr/include/qhull/RoadTest.h
/usr/include/qhull/UsingLibQhull.h
/usr/include/qhull/functionObjects.h
/usr/include/qhull/geom.h
/usr/include/qhull/index.htm
/usr/include/qhull/io.h
/usr/include/qhull/libqhull.h
/usr/include/qhull/mem.h
/usr/include/qhull/merge.h
/usr/include/qhull/poly.h
/usr/include/qhull/qh-geom.htm
/usr/include/qhull/qh-globa.htm
/usr/include/qhull/qh-io.htm
/usr/include/qhull/qh-mem.htm
/usr/include/qhull/qh-merge.htm
/usr/include/qhull/qh-poly.htm
/usr/include/qhull/qh-qhull.htm
/usr/include/qhull/qh-set.htm
/usr/include/qhull/qh-stat.htm
/usr/include/qhull/qh-user.htm
/usr/include/qhull/qhull.h
/usr/include/qhull/qhull_a.h
/usr/include/qhull/qset.h
/usr/include/qhull/random.h
/usr/include/qhull/stat.h
/usr/include/qhull/user.h