Author: Jerome Mouneyrac
MDL-30542 backport recent 2.2 changes about security checks
http://git.moodle.org/gw?p=moodle.git;a=commit;h=1aa648116db3208bda4dd56b7fe93250035fb433
http://github.com/moodle/moodle/commit/1aa648116db3208bda4dd56b7fe93250035fb433
+ 2.1 en [filenameexist,core_webservice]
+ 2.1 en [servicenotavailable,core_webservice]