/usr/share/ is in postgresql-9.1-postgis 1.5.3-2.
This file is owned by root:root, with mode 0o755.
..
/usr/share/postgresql/
/usr/share/postgresql/9.1/
/usr/share/postgresql/9.1/contrib/
/usr/share/postgresql/9.1/contrib/postgis_comments.sql
/usr/share/postgresql/9.1/contrib/postgis-1.5/
/usr/share/postgresql/9.1/contrib/postgis-1.5/postgis.sql
/usr/share/postgresql/9.1/contrib/postgis-1.5/postgis_upgrade_14_to_15.sql
/usr/share/postgresql/9.1/contrib/postgis-1.5/postgis_upgrade_13_to_15.sql
/usr/share/postgresql/9.1/contrib/postgis-1.5/uninstall_postgis.sql
/usr/share/postgresql/9.1/contrib/postgis-1.5/postgis_upgrade_15_minor.sql
/usr/share/postgresql/9.1/contrib/postgis-1.5/spatial_ref_sys.sql
/usr/share/doc/
/usr/share/doc/postgresql-9.1-postgis/
/usr/share/doc/postgresql-9.1-postgis/README.Debian.gz
/usr/share/doc/postgresql-9.1-postgis/copyright
/usr/share/doc/postgresql-9.1-postgis/changelog.Debian.gz
/usr/share/doc/postgresql-9.1-postgis/changelog.gz
/usr/share/postgresql-9.1-postgis/
/usr/share/postgresql-9.1-postgis/utils/
/usr/share/postgresql-9.1-postgis/utils/postgis_proc_upgrade.pl
/usr/share/postgresql-9.1-postgis/utils/README
/usr/share/postgresql-9.1-postgis/utils/test_geography_estimation.pl
/usr/share/postgresql-9.1-postgis/utils/postgis_restore.pl
/usr/share/postgresql-9.1-postgis/utils/test_geography_joinestimation.pl
/usr/share/postgresql-9.1-postgis/utils/read_scripts_version.pl
/usr/share/postgresql-9.1-postgis/utils/test_estimation.pl
/usr/share/postgresql-9.1-postgis/utils/create_undef.pl
/usr/share/postgresql-9.1-postgis/utils/profile_intersects.pl
/usr/share/postgresql-9.1-postgis/utils/new_postgis_restore.pl
/usr/share/postgresql-9.1-postgis/utils/test_joinestimation.pl