Backport: r1835287

Review by popcorner with further edits for clarity by both CodeingBoy
and popcorner, their discussion at https://github.com/popcorner/chect/pull/1

Added CONTENT_LANGUAGE variable for both translations.

Note user-visible update in CHANGES



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1835289 13f79535-47bb-0310-9956-ffa450edef68