Hooks into the file API (backport of MDL-57476)

From MDL-57476 's testing instructions: Breakout your favorite editor. Add these lines to mod/forum/lib.php: function forum_after_file_created($file) { debugging('forum_create_file'); var_dump($file); }   function forum_after_file_updated($newfile, $oldfile) { debugging('forum_update_file'); if ($newfile->timemodified == $oldfile->timemodified) { throw new coding_exception('fail'); } var_dump($newfile, $oldfile); }   function forum_after_file_deleted($file) { debugging('forum_delete_file'); var_dump($file); } Drop the attached file_hooks_test.php into the root of your Moodle. Run file_hooks_test.php on the CLI, e.g. php file_hooks_test.php You should see that the three forum hooks are called.