/usr/share/ is in postgresql-9.5-pgmemcache 2.3.0-2.
This file is owned by root:root, with mode 0o755.
..
/usr/share/postgresql/
/usr/share/postgresql/9.5/
/usr/share/postgresql/9.5/extension/
/usr/share/postgresql/9.5/extension/pgmemcache--2.1--2.1.1.sql
/usr/share/postgresql/9.5/extension/pgmemcache--2.2.0--2.3.0.sql
/usr/share/postgresql/9.5/extension/pgmemcache.control
/usr/share/postgresql/9.5/extension/pgmemcache--unpackaged--2.0.sql
/usr/share/postgresql/9.5/extension/pgmemcache--2.0--2.1.sql
/usr/share/postgresql/9.5/extension/pgmemcache--2.3.0.sql
/usr/share/postgresql/9.5/extension/pgmemcache--2.1.1--2.1.2.sql
/usr/share/postgresql/9.5/extension/pgmemcache--2.1.2--2.2.0.sql
/usr/share/doc/
/usr/share/doc/postgresql-9.5-pgmemcache/
/usr/share/doc/postgresql-9.5-pgmemcache/README.rst.gz
/usr/share/doc/postgresql-9.5-pgmemcache/copyright
/usr/share/doc/postgresql-9.5-pgmemcache/changelog.Debian.gz