/usr/share/postgresql/9.5/extension/plr.control is in postgresql-9.5-plr 1:8.3.0.16-1.
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 | # plr extension
comment = 'load R interpreter and execute R script from within a database'
default_version = '8.3.0.16'
module_pathname = '$libdir/plr'
relocatable = true
|