Author: Matthew Noorenberghe
MDL-41634 - URL Download Repository doesn't warn when asked to download non-image files
http://git.moodle.org/gw?p=moodle.git;a=commit;h=9b3d60fc47e4db8956174a600a7c21b0ea453f86
http://github.com/moodle/moodle/commit/9b3d60fc47e4db8956174a600a7c21b0ea453f86
+ 2.6 en [validfiletype,repository_url]