Author: Dan Poltawski
MDL-32134 lang: Add missing PNG string
http://git.moodle.org/gw?p=moodle.git;a=commit;h=252979a7872155c39edbd6b3aa1f411d0b41213a
http://github.com/moodle/moodle/commit/252979a7872155c39edbd6b3aa1f411d0b41213a
+ 2.1 en [image/png,core_mimetypes]