/usr/share/postgresql/9.4/extension/xml2.control is in postgresql-contrib-9.4 9.4.18-0+deb8u1.
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 | # xml2 extension
comment = 'XPath querying and XSLT'
default_version = '1.0'
module_pathname = '$libdir/pgxml'
# non-relocatable because xml2--unpackaged--1.0.sql needs to use @extschema@
relocatable = false
|