fix non allowed string concatenation in lang file
Signed-off-by:Eric Villard <dev@eviweb.fr>
add related issue reference on the Moodle issue tracker

https://tracker.moodle.org/browse/MDL-32791
Signed-off-by:Eric Villard <dev@eviweb.fr>
add link to the list of provided fixes
Signed-off-by:Eric Villard <dev@eviweb.fr>