/usr/include/libical/ is in libical2-dev 2.0.0-4.
This file is owned by root:root, with mode 0o755.
..
/usr/include/libical/ical.h
/usr/include/libical/icalarray.h
/usr/include/libical/icalattach.h
/usr/include/libical/icalcalendar.h
/usr/include/libical/icalclassify.h
/usr/include/libical/icalcluster.h
/usr/include/libical/icalcomponent.h
/usr/include/libical/icalderivedparameter.h
/usr/include/libical/icalderivedproperty.h
/usr/include/libical/icalderivedvalue.h
/usr/include/libical/icaldirset.h
/usr/include/libical/icaldirsetimpl.h
/usr/include/libical/icalduration.h
/usr/include/libical/icalenums.h
/usr/include/libical/icalerror.h
/usr/include/libical/icalfileset.h
/usr/include/libical/icalfilesetimpl.h
/usr/include/libical/icalgauge.h
/usr/include/libical/icalgaugeimpl.h
/usr/include/libical/icallangbind.h
/usr/include/libical/icalmemory.h
/usr/include/libical/icalmessage.h
/usr/include/libical/icalmime.h
/usr/include/libical/icalparameter.h
/usr/include/libical/icalparameter_cxx.h
/usr/include/libical/icalparser.h
/usr/include/libical/icalperiod.h
/usr/include/libical/icalproperty.h
/usr/include/libical/icalproperty_cxx.h
/usr/include/libical/icalrecur.h
/usr/include/libical/icalrestriction.h
/usr/include/libical/icalset.h
/usr/include/libical/icalspanlist.h
/usr/include/libical/icalspanlist_cxx.h
/usr/include/libical/icalss.h
/usr/include/libical/icalssyacc.h
/usr/include/libical/icaltime.h
/usr/include/libical/icaltimezone.h
/usr/include/libical/icaltypes.h
/usr/include/libical/icaltz-util.h
/usr/include/libical/icalvalue.h
/usr/include/libical/icalvalue_cxx.h
/usr/include/libical/icalvcal.h
/usr/include/libical/icptrholder_cxx.h
/usr/include/libical/libical_ical_export.h
/usr/include/libical/libical_icalss_export.h
/usr/include/libical/libical_vcal_export.h
/usr/include/libical/pvl.h
/usr/include/libical/sspm.h
/usr/include/libical/vcaltmp.h
/usr/include/libical/vcc.h
/usr/include/libical/vcomponent_cxx.h
/usr/include/libical/vobject.h