Author: Marina Glancy
MDL-50887 antivirus: clamav is standard plugin, missing strings
http://git.moodle.org/gw?p=moodle.git;a=commit;h=d2de503c805123869fc9d93841dd3afdf4b83192
http://github.com/moodle/moodle/commit/d2de503c805123869fc9d93841dd3afdf4b83192
+ 3.1 en [type_antivirus,core_plugin]
+ 3.1 en [type_antivirus_plural,core_plugin]