MDL-41820 XSS in the quiz responses report.

Thanks to Michael Hess for finding this bug and reporting it to us.
MDL-41941 clean message text
MDL-41807 repository_filesystem: Prevent access to parent directories
MDL-38743 add private cache headers
Automatically generated installer lang files
Merge branch 'install_23_STABLE' of git://git.moodle.org/moodle-install into MOODLE_23_STABLE
weekly release 2.3.9+