Author: Dongsheng Cai
MDL-26388, pop up a dialog when attaching a file already being used in draft area.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=9fb4a6300bdf03288e00a6738ea82728b7d9df61
http://github.com/moodle/moodle/commit/9fb4a6300bdf03288e00a6738ea82728b7d9df61
+ 2.0 en [fileexistsdialog_editor,core_repository]
+ 2.0 en [fileexistsdialog_filemanager,core_repository]
+ 2.0 en [fileexistsdialogheader,core_repository]
+ 2.0 en [overwrite,core_repository]
+ 2.0 en [renameto,core_repository]