Author: Andrew Robert Nicols
MDL-32142 Add missing langstring for section backups
http://git.moodle.org/gw?p=moodle.git;a=commit;h=07435fc1173ad4c6a903642b01747cfe6a514ec2
http://github.com/moodle/moodle/commit/07435fc1173ad4c6a903642b01747cfe6a514ec2
+ 2.2 en [backuptypesection,core_backup]