/usr/include/ql/termstructures/credit/ is in libquantlib0-dev 1.7.1-1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/ql/termstructures/credit/all.hpp
/usr/include/ql/termstructures/credit/defaultdensitystructure.hpp
/usr/include/ql/termstructures/credit/defaultprobabilityhelpers.hpp
/usr/include/ql/termstructures/credit/flathazardrate.hpp
/usr/include/ql/termstructures/credit/hazardratestructure.hpp
/usr/include/ql/termstructures/credit/interpolateddefaultdensitycurve.hpp
/usr/include/ql/termstructures/credit/interpolatedhazardratecurve.hpp
/usr/include/ql/termstructures/credit/interpolatedsurvivalprobabilitycurve.hpp
/usr/include/ql/termstructures/credit/piecewisedefaultcurve.hpp
/usr/include/ql/termstructures/credit/probabilitytraits.hpp
/usr/include/ql/termstructures/credit/survivalprobabilitystructure.hpp