/usr/share/postgresql/9.5/extension/pltclu.control is in postgresql-pltcl-9.5 9.5.2-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 | # pltclu extension
comment = 'PL/TclU untrusted procedural language'
default_version = '1.0'
module_pathname = '$libdir/pltcl'
relocatable = false
schema = pg_catalog
superuser = true
|