Author: Ankit Kumar Agarwal
MDL-29619 Validate urls before generating output
http://git.moodle.org/gw?p=moodle.git;a=commit;h=49b266c07bfa8e0622a2b515631addbb05560f8d
http://github.com/moodle/moodle/commit/49b266c07bfa8e0622a2b515631addbb05560f8d
+ 2.1 en [invalidstoredurl,mod_url]