get_save_file_name - back up editor file on abnormal exit
string get_save_file_name( string );
This master apply is called by ed() when a player disconnects while in the editor and editing a file. This function should return an alter‐ nate file name for the file to be saved, to avoid overwriting the orig‐ inal.
This apply used to be named get_ed_buffer_save_file_name().