bug#27986: 26.0.50; 'rename-file' can rename files without confirmation

[Eli Zaretskii]

> From: Andy Moreton <andrewjmoreton@gmail.com>
> Date: Tue, 15 Aug 2017 13:45:02 +0100
> 
> ../../src/fileio.c: In function 'Frename_file':
> ../../src/fileio.c:2300:41: error: duplicate case value
>   case EEXIST: case EINVAL: case ENOSYS: case ENOTSUP:
>                                          ^~~~
> ../../src/fileio.c:2300:28: note: previously used here
>   case EEXIST: case EINVAL: case ENOSYS: case ENOTSUP:
>                             ^~~~

Should be fixed now.