Author: Andrew Nicols
MDL-44241 atto_unlink: Merge into atto_link
http://git.moodle.org/gw?p=moodle.git;a=commit;h=49a510efbd4b620d46bebda17f6bbe05df6dc503
http://github.com/moodle/moodle/commit/49a510efbd4b620d46bebda17f6bbe05df6dc503
+ 2.7 en [unlink,atto_link]